My ds1 who is 6 1/2 has only come out of pull-ups at nighttime in the last 3 months. He was a very heavy sleeper, and a very heavy wetter at night. We tried a few times, but it never stuck and he'd get upset by it.

In the end hubby ended up getting into the habit of taking him to the toilet around 10:30-11pm each night, asleep or awake, we did this for about a month, then oneday he forgot and ds woke up by himself to go. We haven't looked back since!