Rooms are assigned a few day before you arrive, but they can change right up till the moment your CM prints out your keys. How you made your ressie will make very little difference in whether or not you request is honored, it is simply a matter of trying to honor as many as they can with what rooms they have available at the time. Lets say you want a first floor room in building A for a check in on Tuesday and another guest has only requested a room in building A for that day. If only one room is available in building A for Tuesday guest 2 might get that room while the room assigners will give you a first floor room in building B. They have done what they can to make you both happy, but the rooms were jsut not available to fill all requests. If you find the room you are givin really doesn't work for you, you can always ask to be moved if a room more to your liking will be available in a day or so(if you are going to be there for a few days)