When my class started vet school, they told us to plan to study for 4 hours a night.

If class gets out at 5, that means studying will last until 9 pm minimum. I would have already gone totally insane if I studied 4 hours a night.
I am, however, trying to stay more on top of things this year. I try to review notes from class for about an hour or two. So far it's manageable, but I know it won't last. Usually about midway through the semester I end up dedicating one night to a certain subject, and playing catch-up on the weekends. It may not be the most efficient system, but it works for me.