Hey brother it all depends on the levels in your tent and what you are trying to attain . I ran mine on a timer and fan speed dial regulated. I had mine going on every 10 min when they were in vegetative and pre flowering.. when they hit flowering to keep the levels good like my heat and humidity I kept her going 24/7 but set the speed of the exhaust fan at a lower level but ran her 24 /7 and it did great it's all about what your girls want it isn't always necessary to run her like that what your doing every three minutes is fine just harder on the fan when you keep tripping her on and off hope that helps at all. Cheers