I've left my guns both flint and cap loaded for a month or more with no trouble. On the flinters I use a leather stall on the frizzen having seen one go off with no prime and the cock being dropped on the frizzen and on the caps I remove the cap and place a piece of lightly oiled leather on the nipple before lowering the hammer. The flinters will have a small feather in the vent hole which will swell with humidity and shows it's loaded. Before I try to shoot either type I run a small Brasswire through the vent and pull the nipple on the cap to loosen the powder charge with the Brass wire. Note that is a Brass wire.Charges will pack down tight if left for some time. Hope this helps.
Rock Lock