I'm a long term dummy user (around 8 hours every night) and sometimes I feel strain on my front teeth. It goes away though an hour or so after I take my dummy out in a morning.
I wish I could say that I never stopped but I remember them going in the bin when I was 2 so I'll say 5 to 10. Not too long after I started wanting one again, so if any ever got left at my house when my parents friends brought their babies around I would get them, hide them and use them in...