K.F.
Well I may be out of the majority, but I have two avid thumb-suckers and the magic age for us is 4. I feel like it is a self-soothing device and the dentist has said it isn't effecting either of their teeth. I believe in picking my battles. At 4 you can reason with them. We have a now 7 year old and at 4 we started to ween (sp?) her. We started with only letting her suck her thumb at home, then we limited it to her bed (she had to go sit on her bed if she wanted to suck) then just for bedtime. Allowing her to go sit on her bed and suck was a beg help for us because it made it her choice to stop. My 3 year old is still sucking her thumb but I can already tell she is doing it less and less - and it's a good signal to us that she is tired or upset. Good luck with whatever you do!