The plant needs light to process the chlorophyll. 2 weeks of dark can harm them even at the end of the cycle with out light they will not grow. You can take it down to 10 light on but less then that and you are missing the point. Plus you need the light to help the plant use up stored chlorophyll and remove that taste. You do stop feeding them N the last 2 weeks to make them used up the food they have stored. That speeds up the curing process as well.