We have the opposite with our 7 year old SWCAH daughter, in fact she is always first asleep at night ahead of her two younger sisters.  It is the youngest one (4 years old nonCAH) that goes to bed and takes a while to get to sleep, always complaining that she "isn’t tired".  Having said all that, when I was on dex during my 2nd and 3rd pregnancies, I had a lot of trouble sleeping, would lay awake in the middle of the night wide awake, not tired and not able to get back to sleep!