On a somewhat less pessimistic note...
I got into the building at seven in the morning, walked out of the building around four, four-thirty in the afternoon. Sometimes I'd come back for an hour or two to stand my night study watch or give a friend some help reviewing materials; other times I showed up to make my mandatory study hour requirement. And yes, you'll have one; I was on 10-0's, some people were on 20-3's. Err, which translates to ten hours a week, zero daily for 10-0's, and twenty hours a week, three daily for 20-3's. There are other flavors; I think they were 15-2's and 25-4's. Same theme.
Otherwise, I spent less than - merrily spent less than - ten hours a day in that place. Toss in a couple hours a day for "military stuff" like PT or making sure my uniforms were decent-looking, and I'd say that about half my day was free. Take out six to eight hours for sleep, and you've got four or five hours of free time during the day to do what you want...within the confines of your badge color status. Green dot, I was generally off-base on the weekends right up until curfew. Blue dot, I was generally nowhere near NNPTC during the weekends - there are some nice beaches near Goose Creek, and motel rooms are cheap if you don't want to head back. Double weekends during spring break at Myrtle Beach was awesome.
Of course, all of this is predicated on academic and military performance - maintain the GPA near the 4.0 range, perform well in the military song-and-dance routine, and you will have a lot more freedom and leeway in your actions than Shipmate Screwup who has a 2.6 GPA.