If I were you, I'd take small 15-20 minute breaks per hour. That way, you can continue to study for a total of nine hours, and still have something to look forward to... It works for me! XD
its good idea 20 mins per hour = 180 min in 9h i.e 1,5h and 20 mins break , thanx
study for like 10 or 15 mins take a 10 min break or longer and then just repeat.