Violet and I lived together within a couple months of dating seriously; she just spent more and more time at my place and more and more of her stuff accumulated there, and then her roommates had a blowout and I said "screw it, just move in", lol. That was almost exactly 25 months ago.
Lana moved in a few months later as a friend and roommate; we "rescued" her and moved her in when we dropped her off oe day and saw her terrible living situation. That was about 21 months ago. 7 months ago she joined our relationship "officially" and physically, though she makes it clear that she'd loved us emotioally for a long time before that.
Anne had her own place a couple of miles away for the brief time we dated her.
I bought a house 11 months ago, a few months before Lana became an official girlfriend and before we met Adrian. 4 bedrooms, 2400 sq ft, plenty of room. There was never any question of Lana moving with us or not despite being "just a roommate"; we took her into consideration while house hunting, lol.
Adrian moved in about the same time Lana joined the relationship. It was too much too fast and we're still dealing with the fallout, but it's slowly resolving. I think. Or hope. Or something like that.
Right now Violet and I share the expansive master suite, and the other two have their own rooms across the upper floor, and there's a guest room; it's been this way for more than 7 months now. As finances permit we may be looking into getting Lana and Adrian their own place(s); they alternately adore the idea and chaff at it. It's all up in the air right now, we'll see what happens I guess...