If your DS is not having problems, I wouldn't worry about the 8 hours of sleep a night. The range of normal is fairly broad. All three of my kids routinely sleep about 8 hours a night starting from a younger age. My two 9-year-olds don't get into bed until about 11PM and get up about 7:30 AM. Sometimes I do have to make sure that they actually go to sleep after getting into bed.