I have two autistic grandsons. The older one is now 13, and goes to bed around 8.30 without being prompted. When he was younger he would go to bed at an appropriate time, but wake up around 4 am and sing loudly and chant, waking everyone up. Now he has an alarm clock in his room and knows he doesn't come downstairs till 6 am, and keeps quiet until then. He's always down on the dot though, and amuses himself on his computer. The youngest one is 5 and is following pretty much the same pattern, except that he likes to come downstairs around 6 and climb into bed with mum & dad. It was funny last time we were down there because we were sleeping in mum & dad's bed. In came DGS at 6, snuggled in next to me and then realised. He disappeared like a rat up a drainpipe!! They're both in mainstream education; the older one is at a great school in Oxford that has a unit, to which he can go and chill if things get stressful.