Re: TS3: Do Sims age up when on other worlds?

@escapedpolarbear  Every time you start a new game, you're also loading a new instance of that world.  So you could play Sunset Valley, for example, in as many different ways as you'd like, and each one would be independent from and uninfluenced by the others.  Any families that you placed in a previous save would not be present in the new one.

Within a save, you can have aging on or off globally, and it will apply to every sim in that town.  If you'd like your current family to age while others don't, you can turn aging off and use birthday cakes to force an age transition on a particular sim whenever you're ready.  Some people who play rotationally do this without issue.  Others will turn off aging while playing all but one family within the rotation (i.e. spend a week with each of five households, and turn on aging for only the fifth week, then turn it off again when you go back to the first family).  This way, the sims get older in proportion to the time you spend with them, and unplayed townies will age as well.