You might be adding salt too rarely if: dishes have spots, your skin feels dry, or your laundry smells like a dishrag. That’s your softener whispering, “Feed me, Seymour.” Add salt. If it happens every two weeks, you have your frequency.
You’re adding salt too often if: the tank is full but never seems to drop. Or if you see water seeping over the salt line. That’s a sign of a salt bridge—break it up. Or your softener might be regenerating too often. Call a plumber if you feel out of your depth (pun intended).