As primarily being a deer hunter, I start each season with a new flint, and of course I check it a time or two, or three just to be sure.
After that the hammer may fall several times and usually the season is over. Usually, not always. But I cannot remember ever having to install a second new flint.
Then I will use that flint far into the clubs once a month primitive shoots of approx. 12 shots each shoot. Sometimes the flint will last until the next hunting season with some sharpening.
And here is a question for those who know....
Usually if I seem to be loosing my spark I just open my frizzen about a quarter way, cock and pull the trigger. (gun unloaded) This seems to really sharpen the flint. I have often wondered though if I might be damaging the lock, though never seems to.
It is a nasty collision, but never fails to sharpen the flint