So I read up about how people aren't doing night-training anymore because you're just meant to wait until your kid is 'ready' and the nappies go dry for a week. Have just made the switch to no nappy dry nighttimes with DS at 3.5 years. Turns out though that he was ready months and months ago, but is just too lazy to NOT wee in a nappy if he is wearing a nappy. In fact, if he is having too much fun playing, he will still sometimes wee himself during the daytime, again because, and I quote, "I'm too lazy to go the toilet." So yeah, sometimes you just have to guess and try the underpants when they're still wetting heavily at night (depending on how lazy your kid seems).