I'm in a few bands. On the covers & function side I have to prioritise Friday and Saturday nights for earning decent money, so pub gigs on those nights will get depped out. Any other night is usually on a first come first served basis. My originals band works daytimes so no conflict there. I'm a full time player, and depping on & depping out gigs is the norm. Yes there are some bands that don't like it, but on the whole it's accepted as part of life in this business. It also helps keep us all from going nuts playing the same songs with the same people night after night, I love the variety.
I'd say that maybe once every 2 or 3 years I have a problem with a double booked night that causes me a headache.