nothing lasts forever...
the more you shoot an old gun the sooner the old wood will crack and the metal parts will fail...
BS!
I have a Joseph Lang non-rebounding hammer gun completed March 6, 1866 and rebarreled in Damascus by James Woodward around 1872.
I've shot over 6,000 of my reloads and RST cartridges in it since I've owned this gun with no damage to wood or metal and have made no repairs. And I will continue to shoot it in the future and fully expect to leave it in shooting condition to my grandson or granddaughter, whoever wants it the most.
Well made old guns will stand up to multiple human lifetimes of shooting, provided the gun is not abused by an idiot.