Our two (3y, 1y) have been in the same room for about 2m. It was ds's room, and dd moved in at about 11m. He had been quite happy to stay in his cot, wasn't especially interested in a 'big bed', and we encouraged that, because I thought it would be easier to have them both in cots once they were both in the same room. I think you've proved me right! Ds was a bit jealous at first, but he seems to have accepted it now. So far it's gone well, and when I hear them talking I simply pop my head in and say 'Quiet now, no talking, time to go to sleep. Good night' and it works. I don't know what I did to deserve them! I don't know how you can prevent the partying, but perhaps you need to police them a bit more, and stop the fun and games earlier. It's easy for me, because their room is opposite the kitchen, so I can hear them (if they talk) while I'm clearing up from supper.