The length of how long a flint will last has so many variables it is hard to say. I have knapped them and got 60 shots off one Thomas Fuller Flint. Then again, I have put a new flint in, got maybe ten shots, and had it split right down the middle. If you knapp the flints you will of course get many more shots off them. I had an Agate that I got so many shots off it, I stopped keeping track.

When I hunt with a flintlock, I always have a new flint that I strike to the frizzen twice before I hunt with it. Then I know the edge is formed and it will go off real fast and normally 99.999% of the time if the pan powder is dry.

Buy some alcohol swabs at the pharmacy. They come pre wrapped in a pack of ten. I carry a couple of them when I hunt and from time to time will take one of them, blow the pan clean of powder, wipe the frizzen, the flint edge, and the pan, let it all dry, and then put new powder in it.

The other day I was shooting in a snow day on my range to see what makes the flintlock fail. I had a new flint and was shooting 3f as my pan prime. I have no idea what makes a flintlock fail in the bad weather as it behaved very well. It acted like the weather was nice and dry. I use a Thomas Fuller Black English Flint and was shooting a Lyman Trade Rifle at the time.