I'm on approximately generation 5 at this point but I'm now playing a rotation with almost 200 sims, so time is going a little bit slower now. It's kind of a rotational legacy because they do age out.
If I just played one family, I'd be a lot farther along. I played nearly all of TS2 with one family. I think I was on the really long life span, it took a long time to age up. In terms of actually playing just one household, that was the longest. The family wasn't based on me, it was random but I guess that I liked them. They were very much a functional and happy family. I remember being sad to leave them behind at the time.
I played TS3 at about 3 different intervals, maybe more than that. I think I tended to start up new saves a lot.
I guess I could try to add that TS2 family back into my rotation sometime, like my own pre-mades.