my son is nearly 4, no matter how I try, he only sleeps around 10 hours each day, including nap. I tried to put him to sleep earlier, but he just lay down on the bed for 1 hour, and fell asleep at his expected sleeping time, exactly 10 hours for that day!
My son since 3.8 years old only sleep 9 hours (9:30 to 7:00) a day. Actually he should have 1.5 hours sleeping time at school, however, he cannot fell asleep. I do not know if it is good for him or not.