Hey there, actually there is something like light stress for autos, even with correct intensity and distance, more than 12-14hours causes some kind of light stress, if you're doing 18 hours or more you will find light stress, and if you reduce the light schedule it will be less stress. That's why i do believe that theoretically 12-4-12-4 could be better , especially if you use the IR spectrum to make the plants "sleep" faster, even 8-4-8-4 works, actually if you look at some growers and some research they do say that they are doing this kind of thing. Hope this helps ! 🚀