Depends on humidity, lubricant, etc.
I take pretty good care of my BP revolvers and shoot them much and often, but I do not completely tear them down for cleaning after each shooting session or copperhead / snapping turtle / rabbit shooting either.
I tend to play it by ear, so to speak, and if the internals start to operate sluggishly, then I do the teardown. This is usually after a couple of hundred rounds or more. Less in cold weather.
My rust issues have been infrequent and very minor after thousands of rounds fired.
If I did the complete teardown everyday I shot them I would shoot them less because of the hassle.
I bought them to use - a lot.
For fun, and as working guns.
I don't necessarily expect my BP revolvers to last forever any more than I expect my weedeater or car to.
If any of my revolvers gets to the point it needs to be replaced, I will just buy another one.