The answer to this is: it depends
As a freshman, you only have something like 5 passes a semester (more if you are on one two or three merit lists or if your squadron is number one) so you really don't have a lot of opportunity to go do anything. Also, as a freshman, you are frequently "restricted" to either the base or cadet area (usually due to some form of failure as a class). Also, you can only go out on weekends, not weekdays. The exception to this is if your element or flight organizes a "dining out" then you get to put on service dress and go eat dinner with your squad mates.
As a sophomore not much changes. You have a few more passes, but are still limited to weekend excursions. Junior year is when you can leave during the week (but return by 1950ish for ACQ, and I say ish because that is when it was, the schedule of calls keeps changing) have a car, and you have enough passes to leave. Senior year you can be out till taps (2300 now I believe) and have PLENTY of passes.
Now for the it depends part, it is really major and activity dependent. My freshman and sophomore years I was on the tennis team, so between that and classes I was lucky to sleep and free time was not something I had any of. Because of my majors (physics and math) when I got to junior year, I spent pretty much all my time studying (close to 6 hours EVERY NIGHT) because I was taking 4 hard physics classes at a time and shooting for grad school. That is one scenario. The other is the management major who has their study habits either figured out or doesn't care too much, then there is plenty of free time, or in between. It's all about striking a balance between getting the grades you want and living the life you want. For me, I cared much more about learning as much as possible and getting into a grad school program than I did about my social life, but I was "abnormal" even for a cadet.
Common cadet activities include weekend ski trips, going to a sponsor's or local friend's home, dancing/sporting events in denver, and all sorts of social activities I never had a chance of going to. There are also a lot of good clubs like archery and mountaineering as well as swing dancing and blues night
I played in the cadet orchestra and the show choir band to keep myself from going crazy.
