When the dents in the metal are too low, or when the grooves on your fretboard cause buzzing.

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1984 Squier Contemporary Stratocaster
1986 Peavey Envoy 110
1967 Kingston Acoustic

When the frets get so low you can no longer play it. You can get a few level and crowns before you have to have it refretted. I played my main guitar for ten years give nights a week. In that ten years time it was refretted twice. I used heavy strings (12's and 13's) and did big bends.

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Your pain is the breaking of the shell that encloses your understanding. It is the bitter potion by which the physician within you heals your sick self. Therefore, trust the physician and drink his remedy in silence and tranquility.-Khalil Gibran