well my 2 went to bed at 7 last night and had to be dragged out at almost 9 thgis morning as i had to get them up for playschool and are so tired now that if they don't doze on the couch i'm putting them to bed at 6.
yesterday they didn't wake til 8.30 and both slept on the couch in the afternoon for an hour.
they're 2 and almost 4, they simply need tonnes of sleep.
so if your ds only sleeps 11/12 hours a night then i would imagine he's tired as he's not getting enough sleep
as for behaviour, you simply can't allow a child to behave badly on the grounds of being sick/tired/differant, the rules shoudl be there for a reason, ie; safety or respect for others and leniancy because he's tired is absolute nonsense.
when dd acts up because she's obviously tired she gets tucked into bed and told to come down when she feels better, she either dozes off or lies down for a while and comes down to cuddle me... and this is a child who wets herself if we try to put her in a time out!