You can backflush as often as you like with plain water, every time you make coffee if you like, it won't hurt a thing. Backflushing with detergent is a different story. The frequency that you should backflush depends on how much coffee you make each day. For example, if you work in a coffeehouse making hundreds of espresso drinks per day, you should be backflushing nightly. However, if you are a home user making between two and six shots per day, I only recommend you backflush with detergent no more than once every two to four weeks.