It is not the amount of time that is important but the quality of time.
When I started I thought three hours a night was fine. I soon found out that after a couple of hours the third hour was a waste of time because I was tired.
Try it out for yourself. Dont be too worried about counting the hours. If you worried about the Distance learning timesheet you need to complete then put any thing on it.
The aim is to learn and the time that takes varies with everyone.