I had just one guitar for the first fifteen years of playing, and I play 11s or 12s with a pretty heavy hand. I have found I need to touch up the frets every two-three years. That first guitar got a refret after about fifteen years, then another a couple of years ago when I’d learned how to do it a little better and got some better tools. I am lucky though in that I have really, really dry hands. Never seem to get gunky strings, and I can always tell when someone else has played my guitar. I wonder if the clamminess that eats through strings also affects frets...?