Over revising is a problem. I'd say 2-3 hours a day is the best, 1hr minimum. Revising 6 hours with small breaks isn't great as 40 minutes is usually the average limit for how long a person is concentrated on something. I'd add a bit of exercise or go on social media every so often.
Past papers is the best option followed by questions in general. Then I'd say recalling information without any help and see where the gaps in your learning are.