With the use of salt based nutrient there becomes a risk of build up when using improper watering techniques and it is not common practice to add a flushing agent as part of your regiment which increases the problem.
My best example: I have 5-5 gallon pots 60/40 mix with flowering plants at the proper Temp and humidity, each pot gets 1.25 gallons of water totaling 7 gallons of water each watering and after runoff I have 2 gallons total of clear waste water. My waste water is the same color going in as the water coming out, I use a flushing agent(sladgehammer) ever 6th watering, (feed, water, feed, water, feed, flushing and repeat) with this practice I have a rare need to do an emergency flush for anything because I don't let the salt buildup up in my medium. At the end of the grow every nutrient in use drops off from week five till week seven with a end of life watering/leeching/flushing for a couple weeks to "clean" my coco.
Most Nute company want to sell you more because it's no bother to them if you dump it down the drain in one form or another. From what I've seen plants can still survive on stored nutrients for 4+ weeks of water only, don't try this peeps Iv got nothing better to do then kill plants and grow small yields.
So technically I flushed every other watering and have for a long time, I've tried alternate watering methods, schedules, strengths of nutrients, watering practices and in my grow space this is what works best.
The end goal is healthy plants and maximum Harvest per your space.
Farmall