How much time should I spend studying for the JEE each day?
The ideal time from my experience to study is 4 hours at least daily and give 1 extra hour daily only for solving mock papers (only those questions you have covered). Human attention span is only 45 minutes and you should try to take a 5 minute break after every 1 hour. The break will give your mind the time to recharge and focus again. You can break these 4 hours into two sitting of 2 hours each if you lose focus easily but my advice will be to sit for 4 hours continuously at a time when you are least distracted. Night time after dinner say 9-12 PM is the best time for study considering you have school/coaching in the day time. Mornings are best time to mug things as the mind is fresh, so try to revise formulae/organic chemistry fundae every morning so that it becomes a habit.
If you are focused enough you can easily master one topic in the 4 hour stretch. This is again one of many approaches. You can divide the stretch into 2-3 topics as per your comfort and that too different subject. Again revising what you have studied in the coaching on that day itself is the master key for JEE daily preparation. JEE is all about concepts and once you revise the topic you have studied in coaching you will realize that some concepts are not clear to you even it felt you got it in the coaching. Thus one hour daily should be dedicated in revising the things you have studied in coaching and take help online if you need in clearing doubts immediately.