I did all of those subjects! haha, it completely depends on what kind of learner you are, fortunately for me I remember things quite well so I did no revision apart from a couple of past papers a week or so before the exams and got As.. however if you're aiming for As and A*s my teachers recommended an extra 5-7 hours per week per subject outside of college, so an hour a night per subject and anything extra on the weekends should be fine, it is important to do good quality revision though, not just reading notes for an hour then forgetting them..