Jwith - DD sleeps for 12 hours most nights too. I put her in a boosted BBH Bamboo and fleece cover and that lasts her all night - I'd say she's a medium wetter. She leaks out the back of sposies if have to use them at night but has never leaked out of mu cloth setup but she has a big padded butt. As long as there's no poo and bub doesn't have really bad nappy rash there's nor reason you can't put them in a good night nappy for 12 hours. If your DS is a very heavy wetter you would need to use a full on dedicated night nappy.