I would offer once a week but I also have snakes that will take a f/t medium (or larger) rat if she decides she's not hungry, so I'm not wasting a f/t rat if a picky BP doesn't eat. My big females will eat 2-3 weeks in a row, take a month off, eat every other week, take more time off, etc.

If you don't want to waste feeders you can offer every two weeks.