I just "tested" that. I finished my last duck hunt without firing a shot, and simply wiped down the exterior of my SxS because I planned to hunt the next day. Didn't happen. That was on November 6, and there it's sat ever since.
If I'm going to leave a gun loaded a day or two, I always remove the cap and lower the hammer onto a tab of waxed leather placed over the nipple.
I realized what I had done yesterday when I faced the fact that I'm unlikely to get out again between now and the end of the season on January 22.
I have always had poor luck pulling loads from shotguns, so I drove down to the beach, capped the gun and let fly. Boom! Boom! No misfire and no hesitation. Loads were 80 grains of Goex 2f, 1/8" nitro card, lubed fiber wad, 1 1/4 oz ITX shot, and an overshot card.