Over a period slightly exceeding 50 years I’ve gone through literally hundreds of revolvers – some belonging to me and others to someone else. The guns themselves were anything from brand new to well used, and were made anywhere from the middle 19th century to this current day.
Breakage was limited mostly to flat springs, especially in guns made during the late 1800’s to the 1920’s. I also bought a lot of guns that were broken because as a result the price was considerably depressed. Repairs were usually simple and not expensive.
By far the greatest problems were caused by previous owner neglect, abuse, or home gunsmithing. In particular those caused by someone who with little or no experience or knowledge decided to do an action job, to “lighten up the trigger pull.” After being messed with the gun often ended up in a dealer’s used counter or on a table at some gunshow.
Quality revolvers (Smith & Wesson, Colt and Ruger to name three) seldom break, although I am concerned as we move into an era where the driving motive is to cut manufacturing cost, and therefore possibly quality.
But while I have never been limited to a single gun I’ve never felt the need to have an exact duplicate as a backup. On the rare occasions when something in a carry gun broke I simply switched to something else while the busted one was being repaired. The “something else” could be totally unrelated to the out-of-service revolver, but still served the necessary purpose.
If the revolvers you have are good ones, and not tinkered with, and are properly cared for I wouldn’t worry about duplicating everything unless you worked for an employer that insisted that you had to carry a (whatever) with no exceptions.