Salt tank maintenance

Rain Soft
Model CQC 60C0 20 , system is 7 years old. I have been using salt pellets, but i have had to clean out the salt that packs up at the bottom of the tank. Should the system use close to 100% of the salt? The water level at the bottom of the tank remains constant, but once the salt gets low I break up the salt to keep it loose. I do this before adding more salt. How often should the salt tank be cleaned out? Thanks