I give at least 3 day and it seems to do wonders. First, it is a known fact that chlorophyl will start to degrade in the dark which is good. Also, UV light damages things which is why you don't leave anything you want to keep very long in direct sunlight. If you are leaching (killing) a plant, there is no point to expose it to harsh light. Also, it is possible that old THC is being degraded as new THC is being produced. By putting the plant in the dark you stop this degradation.
The last part is just conjecture but my patients who are unaware of this practise have noticed and commented about a big improvement in product quality. I might actually store a plant in darkness and flushing solution for a week until I'm ready to manacure. Then I hang the entire plant sans leaves upside down until dry and then it goes straight to the bag. No need for curing with this process.
