umm, isn't it more like hours per week? When I'm working (I teach) I have my 35-40 hour work week, plus all the time spent grading papers, adding into the gradebook, lesson planning, making new worksheets - it's probably about 65-70 hours a week. <- Yep, I do give LOTS of homework, projects and stuff to be graded! Then I get home, and have to clean up, take care of DD who's 2, cook for DH, take a shower and hopefully get at least 2 hours of sleep, before everything starts again.
So, I guess: in the summer, I can get 5-10 hours a week, and in winter I get maybe 2-3 hours if I'm really lucky. :)