All I can say is that my almost 6 year old boy has the exact same problem and I have finally determined that it is physiological and not because he's lazy and I've just settled in for the long haul. We don't make a big deal about it but he wears the pull-ups every night and we just act like it's normal for a boy his age to still need a diaper. He really wanted to try without it for a while so I bought a bunch of bed liners and let him try, and took him to the bathroom several times a night and finally, one night as he stood squinting and blinking in front of the toilet I finally asked, "Do you want to just wear the diapers again so you don't have to keep waking up?"

He did and we're still wearing them. Since I know it could be several years before he outgrows it we're just doing our best to keep it from being an issue for him. But he hasn't yet had any sleepovers outside of the family. that part may be tricky