My 15 wk old Ds sucks his thumb to fall asleep, and sucks it pretty often when awake, tho I think this is partly because he is teething. My other children never had nor needed dummies, and I've never really liked them personally, but my mum says thumb sucking is harder habit to break and will make his teeth stick out! However mil positively hates dummies and thinks him sucking his thumb is really cute as my Dh did it as a baby. Not sure what to do! He looks so adorable when he does it, but its not so cute when a big kid does it is it?