The vast majority of people back in the post-CW West were not wealthy enough to afford the latest and greatest. There are two schools of thought about how the average cowhand, farmer, etc., might have cared for their guns. (Most people operating from a fixed base, i.e., a farmhouse, or the bunkhouse of a ranch would more likely have shotguns and or rifles.) Either they would have valued them to the point where they would keep them cleaned and oiled, or, if lazy, they would have neglected them. If you depended on feeding your family or protecting your employer's stock, then I would expect the former. Of course, a gunfighter or lawman, whose very life might depend on the working of his guns, would take good care of them. Wild Bill Hickok is supposed to have practiced with his pistols daily, then cleaned and reloaded them.
I have no idea how good a care he took of his guns, but as a military officer Lt. Fred. H. Beecher would have kept his guns cleaned, oiled and in good repair. Beecher was a "gun nut", having owned a Slocum revolver, a Hawken rifle, and a bunch of other guns, plus a Henry rifle he'd asked his brother to send him. He was apparently carrying the Henry when he was mortally wounded at Beecher Island.
But, I have to agree...100+ years ago, most guns would have not shown 100 years of wear. Maybe nicks, dings, and scratches, but not more than many of us have on our CAS guns. Oh, there is one thing...case hardening will fade to a mottled gray with on exposure to sunlight!