Hello, i wish i had an answer for you but in reality im looking for an answer my self,,,lol.
my son just turned 8 and he still does it. but he only does it when he is really tired watching tv or when he goes to sleep. he has a little bit of an over bit and the dentist said its gonna affect his adult teeth but i dont know what else to do. i tried that nail polish that is supposed to tast nasty, he waited til it dried and put it in his mouth and said, its alittl bit nasty but its ok, and continued to suck away. i tried the taking out of the mouth when he falls asleep but he puts it back in. my brother makes fun of him thinking he will feel like a baby and stop but he dont,, he just says,, i dont care! sooo,, good luck and if you find something that works i would love to hear about !!!
C.