Pete,
What you say about cold affecting things is valid. I know when it's cold up here, and I bring the gun in the house, at times it goes furry all over with the frost coming out of it. When I come in, I push paper towel in the pan if no feather, and stand it on its muzzle.
It seems that as long as the load is in there snug and kind of air -tight, it doesn't seem to matter if the gun has to de-and re-frost.
I think it's the same as metallic cartridges, if the air can't get in they don't fur up on the inside. (I know they do on the outside though!)
Richard.