There's no set amount of generations for this legacy. The goal is to see your family fulfill all 32 (or more) unique Lifetime Wishes, and no wish can be fulfilled more than once.
For all intents and purposes, I recommend creating an entirely new, blank game for this challenge. You may use whatever neighborhood you wish.
1. Make a single young adult in CAS. They can be any gender, look however they want, wear however they want, etc. You may choose their favorite food, music, and clothing. The one thing you have to do: you MUST randomize their traits. I'm not talking about hitting the button until you have a set you're fine with, either. I mean you hit that button once and whatever set you get is what you're stuck with.
Since Lifetime Wishes are the focus of this challenge, you may pick whatever one you want to start with (with one exception, explained under this paragraph). If you don't like the options, you may re-roll them. (For those who don't know, to re-roll your Lifetime Wish choices, just go to Choose Traits and close out the window by hitting X or accept.)
The exception is this (and it applies to all generations from the founder until the final one): if your Sim has a trait associated with a field of study (such as Genius, Green Thumb, Angler, etc), you MUST pick a Lifetime Wish associated with that field. (Examples: a Sim with the Natural Cook trait must pick the Celebrated Five Star Chef or Culinary Librarian Lifetime Wish; a Sim with the Athletic trait must pick Superstar Athlete or Perfect Mind, Perfect Body, etc.) The "Lifetime Wishes" traits relations are pretty obvious, so I won't list them exactly here. Just use your best judgment.
The exception to the exception: if previous family members have already fulfilled all the associated wants, you may choose something different.
2. You may move your Sim onto any size lot, but you must reduce your funds to $1300, the amount leftover after buying the expensive 60x60 lots, in order to make things equal across the board. (If you take the 64x64 lot in Riverview, you may increase your funds to $1300 by using kaching once and then getting rid of the excess funds from that.) This lot is your legacy house, and while non-heirs and spouses may move out at any time, all heirs must live here. You may only move the entire family out of this house if the lot becomes irrevocably bugged.
This is where it gets interesting!
1. No cheats. Seriously. Unless it's to reset a bugged Sim or object, or for advanced building (no, motherlode does not count as advanced building), you are to assume you are not to use it.
2. Spouses: Spouses are eligible to add to your unique Lifetime Wishes tally. You may only have one spouse at a time. You may not marry spouses just to bring them in for their money, then divorce them, move them out, and remarry. You may remarry only when your spouse dies. (The only spouse you are allowed to accidentally-on-purpose kill is the one to fulfill the Gold Digger Lifetime Wish. All other deaths must be natural.) Spouses do not necessarily have to produce heirs, so same-sex couples are totally fine. Spouses are also not necessary, so if you want to play the eternal bachelor/bachelorette Sim, that's fine. If you do marry a Sim into the family, that Sim must take the legacy family's name, whether they are male or female.
3. You must have one blood heir per generation, even for same-sex couples. (However, since you have to jump through hoops to do this, whatever techniques you use to get a blood heir with a same sex couple will be overlooked. This means you can maxmotives to get a cranky man/woman into bed, you can move a woman in to monitor her pregnancy (as long as you move her out immediately afterwards), etc. Also I heard something about men getting pregnant but haven't seen it yet in my game so yeah NO CLUE.)
4. The maximum amount of children you can have for any given generation is 6. Adopted children count toward this limit. Children taken by the social worker also count toward this limit. You are also free to use watermelon/apples to influence the gender of your children as you see fit.
5. You may adopt up to 5 children per generation. Adopted children are not eligible to be heirs, but they ARE eligible to add to the family's unique Lifetime Wishes tally.
6. You may only have one heir per generation, so no double-heir families. Spares are not allowed to be married as long as they remain in the house, nor are they allowed to have children in the house. (They may sow their wild oats out in town however you want, but those children don't count towards the family.) If a spare has a child that is added to the household, the spare and the child must be moved out immediately and that spare is no longer eligible to add to your Lifetime Wishes tally.
The heir must be chosen before the first child reaches Young Adult status. Spares are eligible to add to the unique Lifetime Wishes tally until they reach their Adult birthday, at which point they must be moved out of the house and fulfilling their Lifetime Wishes will not count towards the tally. (This means they have their entire Young Adulthood to work towards the Lifetime Wishes; you don't have to move them out the second they transition from teenager.)
7. The heir MUST have a unique Lifetime Wish. Any child who has a Lifetime Wish previously fulfilled by another family member is ineligible as heir.
8. Each generation MUST fulfill at least one unique Lifetime Wish. This criteria can be met by any eligible member of the family: the heir, heir's spouse, and spares; just so long as it's unique and someone within that specific generation.
9. You cannot fulfill any single Lifetime Wish more than once.
10. Heir-swapping: under most circumstances, once you pick your heir, that Sim is your heir for good. However, you may pick another heir from among the spares if you meet one of the following criteria:
--You thought your heir would end up with a unique Lifetime Wish at some point, but did not. At this point, you may pick another heir.
--If your heir dies and DID NOT HAVE A SPOUSE, you may pick another heir. If the original heir has any surviving children, the heir to the following generation must be picked from them. If there are no surviving children, the children of the new heir are eligible to be next generation heirs. Otherwise, the spouse basically acts as the new heir.
11. You must randomize the traits for every single Sim when you're allowed to pick a new trait. You are only allowed to hit the button ONCE; whatever you get is whatever you're stuck with.
12. You're only allowed to buy the Change Lifetime Wish reward with the heir, and you may only use it in a last-ditch effort to pick up a unique Lifetime Wish. You can re-roll your choices just like in the CAS screen by buying the trait, then clicking the X; you may do that as many times as you wish, as long as you are not spending the points. If you cannot get a unique Lifetime Wish this way, you are SOL.
13. Anything that extends your Sim's lifespan may not be used, such as the death flower to stave off grim, ambrosia, etc.
THE FINAL GENERATION
Your legacy ends when one of the following happens:
1. You win! When you have all 32 unique Lifetime Wish fulfilled, you've won the challenge and your legacy ends.
2. You don't have a blood heir. Whether it's because you never produced one in the first place, or your heir candidates have died and you're unable to produce more, your legacy will end with no one to inherit it.
3. One generation does not fulfill a unique Lifetime Wish. Maybe your family dies tragically in a house fire save for an elder spouse, and that spouse totally can't fulfill that Lifetime Wish in time. Maybe you've reached a point where, like in card games or Mah-jong, you simply have No More Available Moves; if you can't get a unique Lifetime Wish to roll up for the life of you, your legacy is done.
All points are calculated for NORMAL LIFESPAN. However, if you play on a different lifespan setting, tally up your points and:
Short (25 Sim days) : multiply point total by 5.
Medium (50 Sim days) : multiply point total by 2.
Long (190 Sim days) : multiply point total by .40.
Epic (960 Sim days) : multiply point total by .09.
+100 per unique Lifetime Wish fulfilled.
+10 per $50,000 of family net worth.
+20 for each time someone reaches the top of a career NOT associated with a unique Lifetime Wish.
+1 for every skill mastered NOT associated with a unique Lifetime Wish.
+5 for every child born. (+15 for twins, +20 for triplets)
-100 per Lifetime Wish fulfilled more than once.
-50 for every child taken by the social worker.
-50 for every unique Lifetime Wish that isn't fulfilled in time. (The Sim dies, the spare hits adulthood and moves out, etc.)
-100 for every accidental Sim death. (Old age does not count. The point penalty does not apply to your Gold Digger Sim's spouse(s).)
-30 for every demotion.
-50 for getting fired.
-10 for every fire or burglar.
These are rules or modifications to this challenge by ChristinaMay. Thanks, ChristinaMay.
1.Spouses and adopted children are NOT eligible to contribute to the Lifetime Wishes tally. However, they are still susceptible to the point deduction of an uncompleted Lifetime Wish (children only if they remain in the house after YA).
2. (I took out Rule #5-it seemed redundant and Rule #9)
3.If your heir dies but had a child, his/her spouse (if there was one) becomes a "place-holder" for the heir position of this generation otherwise a valid (has a unique Lifetime Wish) spare becomes heir until the original heir's child is older. If your heir died with a spouse but childless you must move out the spouse and pick a new heir from a valid spare. In the case of the spare, the spare would have to complete the Lifetime Wish before moving out when he/she becomes an adult.
4. (11). Added: This includes the Mid-Life Crisis reward.
5.(12). Only the heir is allowed to use the Change Lifetime Wishes reward and ONLY IF he/she and all of the spares have a Lifetime Wish that has already been completed. However you must choose a Lifetime Wish that fits at least one of the heir's traits.
Changed the "-100" for every repeat Lifetime Lifetime Wish to "-20".
Changed -10 for every fire/"burgler" to "burgler who escaped with loot".
Changed -50 per Lifetime Wish unfulfilled to exclude spares and adopted children moved out directly after they aged up to Young Adult.
Source (Credit): http://nene.modthesims.info/showthread.php?t=348587
LIFETIME WISHES LEGACY CHALLENGE RULES