I've gotten rooms as early as 10:00AM and as late as 4:00PM. There is no rhymn or reason. Day of the week and crowd level make the difference--maybe. You can check in early, say 7:30AM, but they do not have to make a room available to you until 3:00 or 4:00PM. In October we waited until after 4:00PM before our room at Pop was ready and it was in the middle of the week. But in December we checked into BWI at 11:00AM and got a room right away and the resorts were at Peak (Dec.10th). It's all in the luck and probably also depends on how many room requests you have on your reservation. We are always very flexible, but always expect that our room will NOT be ready, if it is, then great, if it isn't we just zip off to a park and try later.