71.4 years exactly.
I would imagine so long as you can find opportunities to overcome shyness, I suspect there's never a time you can't overcome it. Considering that I'm 23, I don't really know. I don't think there's a point at which someone should give up, if that's what your asking. However, sometimes I feel like I already have. I don't necessarily describe myself as shy though. I never really liked the word for some reason, although it's probably still an accurate description.