This is certainly a problem for those of us on the spectrum, and in my instance, it has led to a lot of self-medication-- BAD!! !
This overactive brain common among autistics is a chemical condition and while I have not pursued the oft-recommended method of mediation (I can't get my brain to calm down enough for it!), I have tried to use this overactive brain to my advantage. But it can be a real problem when trying to get to sleep at night, because it just doesn't stop-- not at 11 PM, not at midnight, not at 3, 4, or even 5 in the morning... my doctor has prescribed me Klonopin, a benzodiazepine, and Clonidine, a blood pressure relaxant, to help me get to sleep, and so far it's working. So long as you are able to get eight hours of sleep per day, with or without chemical help, then I would say do what I do and use the overactive brain to your advantage.
Check out "Problem Child," my published memoir of life with autism.