Sharpening (knapping) dull flints is actually easy and takes little time to learn. It can double or sometimes triple the life of a flint. I use a copper hammer and knap mine in the cock. Just be sure you're holding a finger under the flint edge and have the cock pulled back from the cock notch otherwise you can damage the notch or sear.
an important point worth taking note of again.
I totally agree Rob!.....I got in my old "flint bucket" to see what I could try to salvage and even attempted to knap a couple in my hand...after a few scratches/cuts I got a set of Vice Grips and after a little careful adjustment...life was much better.
There was a time when I was really anal about keeping up with the number of shots I could get from each flint, by making a note of the number of ball shot that day, etc, etc,...well, long story short, flint life is all about the knapping, nothing else.
And as Hanshi so aptly mention, the learning curve is a short curve, but one that is very necessary for us flintlock shooters.
Jus'sayin.....
Uncle Russ...