Not every couple of months or so--every other week.
No way in HECK!!!! I would definitely say something.... probably along the lines of, "We enjoy visiting with you, but having you visit so often just isn't working out with the other things we have planned. We aren't getting things done that we want to get done."
Next time they call, just say, "I'm sorry but a visit right now isn't going to work with our schedule."