I think the time varies for each person.
Personally, I stay at home on nearly all weeknights and weekends, apart from the occasional Uni party/event and dinner with a few friends/family.
I probably need to be by myself or at home at least 4 nights a week (including holiday breaks). I find social interaction at Uni on the weekdays stressful whenever I bump into people, so I find it relaxing to come back home and not have to deal with any social pressures/obligations etc.