You flush because you want to trigger your plant to be unhealthy right before harvest, oh and to get the extra minerals from your nutes out. Have you ever smoked a bowl and had a FAT pile of ass in the bottom? Whhooops someone didn't flush... Have you ever smoked a bowl where everything turned white and when you tapped it out it almost disintegrated before any of it hit the ground? Hmm, good flush. To me I'd rather not smoke all the shit that leaves all the ASS! Also flushing right before harvest triggers the plant into thinking it's dying, which it is because you quit feeding it. This is good, means that the plant will push everything it took into it's leaves back out and into the buds giving them a last little burst of fattness and flavor. (Since the only thing left in the leaves AFTER FLUSHING is sugars and carbs, the stuff that makes your buds tasty.) Don't flush, I don't care, but I wouldn't smoke your shit.