I think checking in early is best--but if occupancy is high, it probably won't make much difference when you check in--there won't be much to choose from!
Recently stayed at BWI. Checked in around 2pm. Called CRO in advance to list preferences of 2 adjoining, not connecting rooms and any floor except 1st floor.
Ended up being assigned 2 connecting rooms on 1st floor. Changed to 2 rooms on 4th floor 3 doors down from each other. It was not easy to get front desk to change the rooms--even though we hadn't entered them yet.
POLY stayed recently, booked CL garden view--checked in around 7pm (really slow time of year) was upgraded to lagoon view without asking. Was given my 1 preference of being on 3rd floor.
BC stayed recently, booked CL garden view--called CRO got linked reservation numbers for 2 connecting rooms. Checked into BC CL around 11am. No CL connecting rooms available. They allowed me to cancel one room for the 1st night (minors were to occupy their own connecting room). 2nd night on--we were allowed to use the connecting room attached to our 1st night's room without moving anywhere. I thought they handled it well, letting us cancel 1 room the 1st night when a connecting room wasn't available.
WORST experience ever. POP checked in around 2am over Spring Break. Wasn't given any of my listed preferences. Given last room at motel. Bad location and dirty with no where else to go! YIKES!
Checking into CBR at 11:30pm in a few weeks. Booked Pirate room type, but preferenced top floor corner room. Almost sure I won't get it. Traveling during a time touringplans rates crowds at 8's & 9's and checking in late=double whammy!