I all depends (no pun) on how much I wet during that time and how much the diaper will hold. Anywhere from 2 to 8 hours, I guess. I love to have them bulky and moist, so I wait until they're full to the point that they will leak soon.
My earliest memory of being interested in diapers was at age 4 when a 4 year old cousin came to spend the night with her cloth diapers and plastic pants for her bed wetting problem.