What is the end point of a household/game for you?

Well, you'd be right. When I get bored. :D

I really don't think there's really an end to a sim's story until they're dead, and sometimes that's not final either.

I put a save on a long pause (sometimes permenant pause) when I run out of ideas on where to take the story. If I don't revisit a save for more than a few months, I take it as it didn't really mean that much to me, and I delete it.