I use 24 early in veg and during winter. Free heat. My personal observation is that alot of growth takes place during dark cycles and there is a fair amount of posts on the subject. My timer has pins for every 30 minutes and i move em back 1pin a day until I get where I want to be. I havent seen any problems, not for the few autos Ive done. 20/4 seems to be the goto light cycle. Good luck with your grow Jay, any pics?