S.M.
If you go to www.onestepahead.com they have guards for the thumb and fingers. But I say he will probably stop on his own. I have a son who sucks his thumb and he is 2 but he only does it in his crib to fall asleep. He dosen't do it when he is awake at all. I also have a daughter who is 5 and still sucks her fingers but again, only when it is bedtime. Sometimes she does it when she is tired and awake but I just casually mention to take her fingers out of her mouth. Sometimes she stops herself from doing it. I think it is a form of soothing and eventually they will grow out of it. Hopefully! :)