It's definitely doable, I've probably been doing more. I've just finished busy season at work and that was about 12 hour days with an hour commute either side, so that was about 60 hrs a week, 70 including commute. With revision i get out of bed and have no commute so its possible to do a 12 hour day and you get the weekends completely free. unless you want to go hardcore and do 7*12 = 84 hour week, its possible but a killer lol.