My DS11 and DS9 spend a lot of time reading too. I often find DS9 up very early in the morning (4AMishg) reading because he complains there is just not enough hours in the day for him to read on school days and he reads during recess at school too. DS11 is a night owl and stays up late reading books. I wouldn't worry about too much reading as long as they can get their school work completed. I figure there could be a lot worse things they could be doing. Reading is a wonderful habit.