Hi,

First of all you should have relevant intrest in the topic which you are stuying. If you Enjoye your studies you will not get bored with it then you can study for long hours.

Second important thing is that you should have to keep your self physically fit  so that you can spend your energies on studies.

Make a time table -it will help you to manage your studies for long time.

In one of the scientists studies it has been found that studying in small breaks help you to remember faster then studying continuly.

So for better remembering and recalling you can make your time table as such you have a small break of 5-10 minutes after 30 - 35 minutes. In this breaks you can have water,some snacks or fruit or you can Enjoye reading some magzine or the other work you like to do most.

It is essential for long hours studies that you should be physically and mentally fit . So you should do exercise or yoga at leat for half an hour daily to keep your self focused and healthy for studies.

These were few tips to study for longer hours. Hope you will get benefit from this iinformation.