Lucas was born at 34+5, he spent 11 days in hospital.
We were very lucky in the sense that Lucas had quite good size (although he lost a lot of weight very quickly, and wasn't strong enough to be able to suck properly). So even though he was larger than some of the babies which have been born full term (3.01kg) on the forums, he wasn't capable of things like suckling from the breast or bottle, or maintaining body temperature - or for the first few hours of his life, breathing in a normal environment.
He was only in a crib (with oxygen and all the tubes and stuff) for 36 hours, at which point his oxygen retention was fine. I was allowed to have him in my room for the rest of the time until we went home, though a couple of nights they had to bring in the heater, and he was on two hourly obs for the first week (heart rate, temp, etc), and then went to four hourly. And every morning we had weigh ins. We had to keep a diary of his feeds (we had to feed him two hourly initially) and of how much (and how; via gavage or bottle or breast) he'd had.
I credit his fairly early release and lack of problems due to the fact that I had eleven days warning that he was going to be coming early - and on the very first day I went to hospital they gave me a steroid injection, and another one the following morning.
Our release was conditional on the fact that; he took all of his feeds via bottle or breast (he was gavaged- tube fed for the majority of his feeds) for a 24 hour period. And then on top of that, he had to gain and maintain weight consistently.
Our paed didn't really want him to leave the hospital as early as he did (he was 36 weeks +2 days), but the maternity ward staff convinced him we'd be fine and that we'd go back into hospital if anything happened at all. We had to go in each day for the first week for weigh ins, and then after that once a week until we'd been home for four weeks.
I think, in the end - the main answer to your question - is that it depends on the baby!