That will be up to you.
If you believe that running the fans once a day, hourly, or even less is necessary. Some farmers believe that their plants want a steady breeze for stronger growth. Rather than opening the ventilation, you can achieve it by placing a portable fan inside the grow tent. You may also just turn on the in and out ventilation to generate that air movement.
MORE: Do Grow Tents Need Ventilation When Using LED Grow Lights?