I tested this theory with my last grow. Some I purposely did not flush, and fed nutes right up until 3 days before I chopped. I did a nice dry (about a week) then jarred for 2 weeks. The stuff I did not flush, crackled popped and almost sparked every time I took a puff, plus it tasted really chemically with a black ash left. The flushed stuff was fine. not harsh, tasted more of the weed, white ash. After doing my own experiment, I am a firm believer in a good flush. In fact, my current grow just finished week 7. I flushed everything at the beginning of the week, and some strains will go 9 weeks (3 week flush) mighty be a bit overkill, but Oh well.