The gallons of water used between recharges is completely dependent on your personal water usage an programming. The gallons used will constantly flucuate as the internal algorithm learns more about your water use habits.
For a rough estimate, we use the following calculation:
Total softening capacity / hardness concentration in water supply
= approx. gallons between cycles
30,000 grain unit / 25 gpg = 1,200 gallons used between cycles