Once upon a time, I would shoot a new flint until until it became dulled and failed to make sparks, then replace it with a new one. Re-touching the edge with the heel of the frizzen works as a field expedient but the effect doesn't last very long for me. If much shooting is done, it doesn't take long to go though quite a few new flints.
Nowadays I remove the flint after 12 - 15 shots and reestablish a sharp uniform edge across the entire width of the flint using a flint knapping pressure flaking tool. This lets me remove tiny flakes precisely where needed, the flint never gets dull to the point of failure and its use life is greatly extended.
The pressure flaking tool can be made from an antler tine or there are commercially available copper flakers available.
Nowadays I remove the flint after 12 - 15 shots and reestablish a sharp uniform edge across the entire width of the flint using a flint knapping pressure flaking tool. This lets me remove tiny flakes precisely where needed, the flint never gets dull to the point of failure and its use life is greatly extended.
The pressure flaking tool can be made from an antler tine or there are commercially available copper flakers available.