Just once a day but I was brought up to take two. I'm actually surprised at the results, I expected people to be showering more often. Ie: once a week is pretty gross.
What forces me to do it is the feelings of greasy hair, and (if hot) a sweaty face. I can't stand that so triggers shower time.
Being on buprenorphine I really don't enjoy taking showers though, like Burroughs said, 'junkies are like cats, they can't stand water.' It's true.