I do ours about once every two months, but we make coffee only once a day, so maybe would do it every month for yours.
But we have very hard water, and I don't always use Brita-filtered water to make the coffee... it actually tastes better to me made with the hard water. That hard water means lots of scale in the pot.
Remember to run two full pots of plain water through after the vinegar before you make coffee again, unless you like vinegar in your coffee!