Hey guys, here's my experience FWIW...My eldest son was a constant thumb sucker until the age of 9, and nothing we tried over the years helped, including painting his nails with 'Stop', which he just got used to the taste of! We were told he would grow out of it at school, and many do, but he didn't. Taking comforters away didn't help, either, as thumb sucking at night is automatic, and reinforces the habit. In the end, the dentist made us a small brace. It wasn't expensive as it had no orthodontic purpose: it was just to alter the space in his mouth at night so that it wasn't comfortable to put the thumb in. He only had to wear the brace for a few days and he was cured completely: the dentist had advised keeping it in for a few weeks to reinforce the break, but we never bothered as it was obvious that it had done the job. When I consider how much I worried about it beforehand, I cannot recommend the solution highly enough if the habit persists.