What aging game setting do you mostly play on?

I've never played the normal lifespan option for 4. I have tried turning it on and letting it go...but I don't want my favorite sims to die. Especially the family modeled after my own! haha. I am planning on finally aging up my toddler daughter to a kid on her actual birthday this year though. She will be 4, and definitely doesn't act like a toddler sim anymore. But, the kid stage is still a bit beyond a 4 year old I think. Too bad there wasn't a preschool stage. :P