I'd always been a fan of a full 10-12 days flush... just plain water, drain 2 waste. By day 4 or 5 you can see your run-off ppms at 100 or less... mine never get to the base ro level as fig the coir & plants are always bleeding a little something to the flush water. Truly, I can harvest here & no one seems to notice the difference, though I slow dry & cure properly, so... I got it stuck in my head a long time ago about the 10 days, but quite frankly, this may just be exactly that... in my head...?

I will tell you that when I run my nutes (even at lower levels), the buds do swell bigger & fuller... & it is noticeable. If neither you nor your patients can detect any difference, I would run the nutes (at say a 600-700 level) up to 5 days before harvest & water each day d2w till you hit 100 or less. Good to go from here... but slow dry & cure. Best all.