M.K.
Both my children sleep 11+ hours a night without any diaper leaks. I use "Huggies Overnight" diapers on each of them, plus I add a "Diaper Doubler" in the diaper. "Diaper Doubler" is is just like a maxi-pad, but it doesn't have the sticky adhesive. You can find them at Babies R Us (the Dominick's near us no longer carries them).
11-12 hours is a long time to stay in one diaper -- but this worked for us. Good luck!!