It's honestly much better to study in small ten to fifteen minutes sessions multiple times per week as opposed to cram studying. It's way less stressful and the information sticks better. You know how TV advertisements are trying to repeat the same message to you in small chunks multiple times per week? It's the same thing. Our brains retain information way better when its repeated often in small chunks. When you have multiple hour study sessions, the odds are that you're going to be zoning off once the first thirty to forty minutes have passed.