I always shower with my bag off. I like to think that my stoma surrounding skin is getting a good cleaning. I also like the thought that everything is getting some fresh air for a while.
I use 1 piece, so after a good dry with a towel (not my actual stoma - don't want that bleeding), my new bag fits and sticks beautifully.
I am a urostomate, so any form of discharge is no big deal.
I always peed in the shower anyway... LOL