First, I'm curious as to your opinions about borrowing your significant other's toothbrush. I used to think it was really gross. First time my boyfriend offered to lend me his toothbrush, I said outright it was gross, but decided to anyway. Now, it doesn't bother me at all. I always borrow his toothbrush when staying at his place.
Anyway, something makes me think I should just get a toothbrush and leave it there, but I don't know how to go about it. We've never talked about living together or even marriage, and I've always been afraid to bring it up. Leaving something as trivial as a toothbrush sounds like a big leap already. We've been together for more than two years, but I think he's just not ready for that big leap yet. I don't leave ANYTHING at his place, not even a book. The only things we have at each other's places are stuff we've given to one another, not the kind of stuff that you leave when you start treating the place like your home.