What is the importance of having a fan on 24/7?

Photosynthesis. Plants breathe in co2 through the underside of it's leaves. The plant uses up the co2 around the leaf quickly and thats where the oscillating fan comes in to play. It blows away the stagnant co2 depleted air around the leaf and blows in new co2 rich air. Without this exchange the plants growth will slow considerably. The breeze also helps to strengthen stems to help down the road when they need to support the heavy flower weight by increasing the starches in the plant fibers in the stem. Another benefit to air circulation is that bugs down like windy conditions and it makes their life harder and the environment less favorable to set up shop in. Air circulation doesn't need to happen at night so there's no need to have them running during lights out. AC Infinity oscillating clip fans state in their manuals that if you run their fans 24/7 you void the warranty on the product. They need a cool down period. If you choose to run them 24/7 they will eventually start making a knocking sound and eventually the oscillating mechanism will fail and then you have a malfunctioned fan that you spent a bunch of money for but now can't claim warranty on cuz you didn't read the operation manual. So, air movement is pretty important! Hope this gave you some insight.