The more light you can feed your plant and still have it flowering, the higher the yield will be. That's why I start off assuming my plants can handle 13 hours instead of the normal 12. I haven't flowered a strain yet that refuses to flower under 13 hours. For even more light time, check out giving it some 735nm light solely. I haven't seen any experiments yet (though there probably are some), but the theory is that you could increase light times during flower by a couple hours. Too bad those damn 735 LEDs are damn expensive, or I might just try an experiment myself.