Current mids and grads will surely offer authentic inputs. In my observations, plebes during PS will get the most sleep, interestingly enough, because they are so regimented and overseen.
The rest varies with personal discipline, time management, sport commitment, major and ability to multi-task and prioritize.
There are those mids who seem to float through the academics, athletic and military commitments, have a social life, score 7 hours a night, AND sleep between their sheets. The rest - well, you should get some interesting posts. The sponsor mids at our house on the weekend alternate sleeping with homework, laundry and eating.