S.D.
I agree with Mrs. Robinson - he will be ready when he's ready. All kids are different. I have a friend who's son gets up by himself to go to the bathroom in the middle of the night. Whereas my son "holds it" until morning. Our son was potty trained by the time he was 4, but we kept him in a nighttime Pull-up until he was 5. After that we just doubled up on the sheets and mattress pads. That way, if he did have an accident in the middle of the night, we could quickly and easily take off the top layer and he would have a dry layer underneath and could go right back to bed. It's been 6 months now and he may have an occasional accident, but it's rare.