What's the consensus on whether it's possible to keep black powder functional in a cap and ball cylinder under adverse conditions? To my way of thinking, the only real difference between a C&B pistol and one loaded with BP in a cartridge gun is how tightly the cap adheres and seals to the nipple. A conventional cartridge primer has a much tighter fit than a percussion cap but isn't waterproof. In fact, the cap and ball may have an advantage on the loaded end, because the ball or bullet is forcibly swaged into the chamber and typically topped with a bit of grease or a wad.
I've read Hickok fired his revolvers regularly and reloaded fresh rounds with some regularity (perhaps weekly?) but that may have been done out of an abundance of caution - or he may have experienced dud chambers every so often and recognized the potential for a misfire. He didn't live in artificially controlled environments and was subject to whatever Mother Nature had up her sleeve from week to week. Also didn't hurt his marksmanship, since it's logical to assume he wasn't firing blindly into the air (although that is speculation on my part).
About twenty years ago, I loaded an Uberti 1860 Army replica and stuck it in a dresser drawer, then completely forgot about it for 5 or 6 years. I found it one winter when looking from some long johns, then took it to deer camp the following weekend and fired all six. None showed any signs of deterioration but of course, it was stored inside the house for most of that time.
Reason I'm asking is that one of my sons wants to load an 1858 Remington replica I have and leave it wrapped up inside an enclosed tractor cab, just as a last-ditch insurance policy in case he is approached while plowing or whatever. He normally carries a 9mm on his belt when working in the field but sometimes takes it off for maintenance issues, and you never know who might walk up in the middle of nowhere. If you live in south or west Texas, you'll understand who I'm talking about.