B.M.
Hi B.,
From my experience, I have found that actual night time training is more difficult, especially with boys.
My oldest trained early and easily (and his little brother trained the same way), however we are STILL in pull ups at night...he's 5.
TO be able to hold it that long is a physiological thing and some kids' bodies just can't handle it.
We've tried limiting liquids, waking him up before we go to bed and its still hit or miss. We get about 1 dry night a month.
I don't say this to discourage you, but just to say that for some kids its just that their bodies just aren't able to hold it all night.
I wish you luck.
B.