S.C.
Hi J.,
It could have to do with bladder size and growth, he could need more to drink due to his size, but his bladder just hasn't caught up yet, this is definitely a psyiological explanation. However, I stop my 4 and half year from drinking just after dinner (usually dinner is the last drinks of the night), but I do give him a plastic cup with straw half full of water by his bed at night. He potties before his bath. Then I make him go again after he brushes his teeth even if he says he doesn't have to go. I think it's also up to you to keephim going to the bathroom on a reg. schedule. And watch his liquid intake after say 6 p.m. And, he will stop some day I promise! Also, lower you expectations. If he wets his bed for two weeks, so what? He's 4. I also use a mattress pad from Garnett Hill that is waterproof -- he does have accidents.