You can re-grind the firzzens a number of times before they need replacing. They only need re-grinding if they break flints often due to gouges. Keep the top-jaw screw tight, with failry thin leather or lead and you'll get less bounce. Also, some locks have the wrong angle of the cock jaws and strike ahead and smash the flint against the frizzen, instead of scraping down it's face. in the proper arc. The first lock described smashes flints and cuts a quick groove across it's face, while the second's frizzen lasts for thousands of shots.
An 8" grindstone's radus fits most firzzens quite well - apparently, according to Taylor. Remove just enough to smooth out the face.
Some locks will allow reversing the bevel, from up to down, making the flint strike higher, and thus with proper angles, re-cut the frizzen's face when firing. I have two flinters that do that perfectly. When it gts a good groove cut, I reverse the flints and re-cut the face evenly, top to bottom - then go back to bevel up.
I learned all this stuff from him as I'm new to flintlock guns & know little about them but I'm learning, absorbing everything I can.