Mine seem to go about as often as the BP's - maybe once a week or so. A lot will depend on the frequency of feeding as well. Both activities go hand in hand
Neither of my Boas go every other day, maybe its good that yours does.
They might go every few days to a week
I've got two that pee 2-3 times a week, and a couple that pee about every 10 days or so. I think it just depends on the individual snake, and how much water they drink.