Ideally every day would be great! However, as this is most impractical, an adjustment should be made at least 4 times per year. This is easily accomplished by using the water budget or seasonal adjust input found on most controllers. Starting with the default setting of 100%, one may toggle up or down from this number to increase or decrease the overall run times. Or simply install a smart controller with a weather station and let it do this automatically based on weather conditions.