I cannot answer scientifically, only from experience. I have a Joseph Lang non-rebounding hammer gun completed March 6, 1866 and rebarreled about 1872 in Damascus by James Woodward. I have fired about 6,000 low-pressure nitro cartridges (about 500 RST and 5,500 of my equivalent reloads) in this gun without a single malfunction or misfire.
The barrels were honed and Birmingham reproofed in 1990. I don't think that older barrels wear out from use but suffer from pitting caused primarily by corrosive primers.
