You can run them 24/7. It's a matter of preference and can the strain actually handle it. I personally run all my auto flower at 20 hours a day. Seems to be just right. They do seem to like a short break from the lights to recuperate a bit before the next intense growth/bloom session. As you grow more you will learn how the intensity of your led lights is more important during the different stages of growth and flowering. Your more than welcome to check out my current grows for more info on growing autos.👍