We coslept with our twins from birth-- in an odd sort of way. I had been an "accidental" cosleeper with my DD1-- never planned on cosleeping, was kind of scornful about the idea, but then it just seemed so natural. So with the twins, I never even considered doing anything else. We started with me and DH in the queen size, with one baby between us, and one baby on my far side, with a sidecarred crib on that side. We juggled lots of different arrangements as the months went by, ranging from the twins and DH and me and three cats all crammed in a queen-sized bed, with DD1 on a mattress on the floor, to DH on the couch downstairs with DD2, me in the bed with DD1, and DS in the queen-sized all by himself, and everything in between. Whatever was working, at any particular time, to get us all the most possible sleep, while meeting everybody's needs.
We had a sidecarred crib, a portable crib across the room, a twin mattress in the corner, and the guest bed downstairs, all available to us so we could juggle arrangements as needed.
Cosleeping for us seems mostly to come to an end at around a year old-- all of mine were in their own beds by 16 months, and they now sleep in a room all together, each in his/her own bed. (Actually, DD1 coslept for while when the twins were infants, on and off occasionally, I think.) I still have DD1 in bed with me on Fridays, sometimes-- she has a long week at school, and we miss each other, so we like to have a little cuddle at the end of the week-- she's six. And I keep the crib mattress under my bed, to pull out when somebody's sick.
me , he , my three , , and -- and the one we lost