DS would do this early on also, we started putting the next size up on him - if he was wearing a 2 we put him in a size 3 at night. When he got up to size 4, the size he wears now, they sell overnight diapers (huggies overnights in a purple package). His diaper must weigh 10 pounds in the morning, but it doesn't soak through. We did stop the DF at about 7 mo, but now I am so concerned with the hot weather I am constantly offering him water, so he is very wet in the morning.