When do you start playing a new sim?

I play my own homebrew version of legacy challenge, following a family through the generations, so I play Sims until they die...but not at my hands. Usually of old age, but also sometimes due to ... other events.

But I also switch to playing their children as separate households once the children have grown because I don't leave them in the same legacy family house, but rather send them out in the world, so at that point I'm also playing rotational, at least until the older generation dies. Or even after they die if the legacy heir has siblings which I rotate between.