Do you have certain sims you just can't let pass on?

If there is a sim I get really attached to, I save them as YAs to my saved sims and add them to other games to play again and again. Some sims I've played dozens of different iterations of. But I rarely try to extend the life of a sim in a save, because I want to see them live a full and happy life and sometimes that means bringing a nice end to that life.