I have been hunting with the M/L for 35 years and have never had a misfire.I leave mine loaded till the season is over.
If I shoot it and there are several days left in the season I will clean and reload.

I have hunted in the rain , and in cold weather with no problem.I think a lot depends on how well it is dryed and cleaned. if I lived up north where it gets to 0 or below,it may be different.

I am not saying that other people don't clean there guns.it is just that I make sure it is clean and dry,before I load.

if the powder does not get wet in the can,why would it get wet in the barrell??

back to the question : I load the day before the season opens and fire it the day after the season closes , unless I shoot something inbetween.