In the first few years after they discover masturbation, most boys do it much more often than they will in later life. It is not unusual for a boy of 13 or 14 years old to masturbate 3 or 4 times in a day. It's not surprising, therefore, that some boys worry they might be doing it too much. Of course, it's possible that time spent masturbating could be used for more productive activities, but if you're only going to use the extra time for watching television or similar, then don't worry about it. Just enjoy it and you will probably find that in a few years you'll lose the habit.