When I was in school, I took anywhere between 12 and 17 credit hours (averaging about 15), and worked about 10 hours a week. I also did lots of extracurricular activities, especially in my senior year, which probably took up another 10-20 hours a week, more on busy weeks.
Now that I'm not in school anymore, I work anywhere from 40 to 50 hours a week (I think the most I've worked is 3 12's in addition to my other 7 8's in one pay period, so that'd be 44-48 hours a week), plus I manage a non-profit. Since it's November, I'm also writing a novel, and my daily writing takes anywhere from 3 hours to 6 hours, depending on how inspired and diligent I am in writing that day.