That depends; sometimes you may only have 20 minutes. Make every minute count! When doing errands, take along notes you can review (create 3x5 review cards). You will be surprised by how much you can review if you have to wait in line somewhere. Hey, if you have to wait you might as well put that time towards your studies. “What about marathon study sessions?” Marathon sessions for most people do not work. In the short term you might be able to ‘cram’ in all of the information but you will more than likely forget the information long term.