Kind of varies in my experience. Back when I was in the market for a job change they only ran it 3-4 times a year. Usually shortly after fall season, around the summertime, and before fall season. During covid when hiring was constant they switched to doing it monthly, or trying to. Not sure how often they do it now that it has slowed down a little bit.
Just saw one posted at my building with only 5-6 people getting moves, so I assume my building is still doing them fairly often.