If you were to shoot a howdah on a boat, make sure you aim above the water line. I have a howdah make a cartridge using rolling papers, put 3 .319 balls and some lead scraps from casting in there melt some candle wax to hold it all together fold the top and glue it to a dime sized piece of cardboard and ram it on-top of a .600 ball, 35 grains of 777 ff. At close range ouch! game over. But have reliability issues with the howdah cci caps no go, remington fires most of the time, going to have to try some of those tc nipples or maybe the cci magnum.
Where I live in so, cal, I load up cylinders all the time and leave them uncapped some have been sitting for up to 2 months that way, never had a problem, I also keep a couple loaded cap remmys all the time, never had a problem. Make cartridges some sitting for probably 3 months never had a problem. I go shooting 2 times a month, but now I have 12 guns and 17 extra cylinders so some sit for awhile with powder and balls in them. But living on a boat salt air dose bad thing to stuff, you need to experiment.