Dd1 aged 7 goes from 7.30pm to 8am
Dd2 aged 5 goes from 7pm to 8am (both share a room).
Both dds have always needed a lot of sleep.
I have a friend whose dd has about 10 hours a night and has done since she was a baby - she NEVER slept during the day!! HV said some babies just don't need it - she certainly didnt.
I think the advice about not needing to wake them is spot on. If my two have a late night they just sleep in in the morning to make up for it (bless). I know, I know, I'm lucky ....