When I used to manage a front desk for a luxury hotel, I always encouraged people with specific requests to check in around 5pm if possible. Not in an attempt to "buy more time" but mainly because of how the process worked. The room attendants would clean most of the rooms before lunch time, and then after lunch the housekeeping supervisors would then "inspect" all the rooms to ensure everything was as it should be. This meant that there was a mass influx of rooms available between 3 and 5pm, quitting time. We would get many rooms earlier than that, but because many people stay right up until check out time, it was difficult to pull off specific requests before c/i time.