i was wondering how often you should you sharpen a rifle flint
When I'm just shooting a 40-50 shot informal weekend range session, I start with a fresh flint and just go until it misfires...then I clean the frizzen, flint, and pan with alcohol, knapp the flint, and resume.
Or to avoid the eventual misfire, I've sometimes picked an arbitrary number like knapping & cleaning every 10 shots.
Also, just flipping the flint over every other 10 shots between bevel up and bevel down will often have a self-knapping effect.
But if I'm going hunting, I lightly knapp the edge of a new flint at the start, and then again after any/every shot I might take during the season...this year I've shot 4 deer and 1 squirrel on the same flint...lightly reknapping it after each shot so there's no question it will cut the thinnest, hottest shavings of steel off the frizzen for fastest possible ignition.