Update: I was looking at the diapers last ngiht trying to find a lot number that customer service asked for and I noticed that the leg elastics that are supposed to make a seal around baby's legs were all stuck to the edges of the diapers on all the diapers in my package. This is why the diapers were leaking out of the sides as soon as he peed in them - the leg openings were not sealed to hold anything in. Once I unstuck the leg elastics on one diaper and tested it again overnight, it lasted a full 12 hours with no leaks and held A LOT of pee (kiddo was up 4 times that night and drank a little milk each time). So I'm increasing my rating from one star to four (one star off from five for poor quality control that didn't catch the stuck elastics).
Original review: Terrible. We hunted down a package of these overnight diapers to try on our 20 month old who has sensitive skin. (Only one store in town carries the overnight version. I think I know why now.) The first diaper leaked out of the side after 4 hours. The second leaked on the other side after 5 hours. I'm not a fan of changing pajamas and crib sheets multiple times a night and neither is my toddler. I guess we'll stick with the tried and true brand and slather on the aquaphor instead.