Three years? Ish? It's getting hard to keep track with the way I keep jumping into different timelines. And no, we don't really know. We used to think that people went home, because no one ever remembered anyone being missing from their timelines -- and I'm pretty sure that has still held true, but it's possible I've missed something -- but that was before we knew that people could jump from one new world to another instead of going home. It does seem as if our home universe timelines will get picked back up eventually, but that doesn't mean everyone goes home whenever we notice them disappearing.
Just one, at this point, but that's more than some.