DS8 is a third grader who has always been a great sleeper getting about 10-11 hours. He likes to read a good deal before bed and recently has been hooked on a new series.
In the last three weeks, even though we say lights out at 8:30, we found him up reading later and later. Even if he finishes a particular book in the series, he just grabs anything in his room and keeps reading and now he's up until 11. He's been getting about 8 hours but I can't believe this can be enough for him.
He's also started biting his nails again. He has been under some "kid stress" with a piano recital coming up with a challenging piece, he worked hard on an independent study project, he's been trying to do some math enrichment at home to teach himself harder stuff, and basketball season is starting for him. Plus he has his WJ Ach coming up Sunday to try to qualify for DYS following getting qualifying scores on the WISC although I've said little to nothing to him about it. But generally, he has plenty of time for free play, relaxing, hanging with his sister and parents, so I don't think he's feeling overburdened.

Of course, since the days are shorter, he doesn't get as much outside play time as during other parts of the year.

Should I be worried? I am concerned he may be learning unhealthy sleep patterns. When I was his age I did the same thing and had horrible sleep habits.
Can he do well on 8 hours?