PArticle has it right. I will only leave a gun in the bag for a few minutes at most. Also I will oil the gun well before wrapping.
Once the initial forming and boning is complete I take it out of the bag and clean, oil, clean and oil again.
I did one last night for a friends on duty carry piece while he stood there.
Of course with blue guns I tend to let them sit for as slong as I like. I'll have a cigg, go eat dinner, chalenge the wife to a game of spank and tickle....