When either get dull, i sharpen them. I usually sharpen all my new knives once. Usually never have to again. Just one swipe on each side with my Butchers steel keeps them where they need to be after each use. I have no edge retention issues with any of my 440A, 440C, 420HC, 1095, 1085, 1075, 1055, or 5160. I take em out sharp & put em away sharp. Never have to worry if one of mine is sharp or not. Good Knife-Fu to practice. Seriously, i do not find myself sharpening any of those steels very often after first sharpening. Even after hard use, a single swipe on each side is all that is usually necessary.