DS (4 in Feb) normally goes upstairs after Maggie and the Roast Beef (ferocious beast ) at 7.20 for bath, 'puter stories and bed with DH .. so normally around 8ish
gets up around 8 (though sometimes 7.30 and sometimes have to wake him up at 8.30 to get him ready for pre-school) so that'd be 11 to 12 hours and a generally smug-a-mum
(of course vomiting and tummy ache bug meant we were up all night )