Jorge Cervantes says plants can only process 16 hours of light maximum before needing to rest, and after that you are basically just wasting energy. If Cervates says it, I believe it! Also as some have said, plants have had night time for millions of years so it must serve a valid purpose. I used to run 24 hr light but switched to a 16/8 schedule and noticed my roots were much thicker and healthier and therefore my plants were more robust.