I would like to discuss about that. In my short experience whith coco i think that keep the coco saturated at the 90% it's not good at all during veg.
When u start the veg with a cutting, the root system grow faster if we let the coco get dry until 30% of humidity. That dry cycle since the moment you water the coco until 70-80% humidity and gets dry to 25-30% stimulates the root system to grow looking for water when the coco is getting dry.
If we produce many dry cycles a day like 2 or 3, being necesary water 2-3 times a day, we Will be getting a very fast and explosive grow, and a very strong root system.
I only get some run off 1 time a week ir two weeks, and i use enzimes 1 time a week and i'm very happy with my results.
Thats My way of work with coco.
I have followed your method in the past, for the same reasons, but the last grow I changed to regular feeds and have seen a big difference. But I also bottom feed (certain grows like SOG) once into flower through auto feed and air the pots with holes to encourage air pruning. But I always flush through before I switch just in case.
I've never had any issues with pH or salt build up and test the coco regular just in case.
But in coco if it gets too dry the micros will die off, and that's been my main goal this time round, trying to keep the eco life happy.
I'm just a novice and I'm only going from what I've learned, mostly from the farm so please forgive my ignorance on some subjects...
So for all I agree with Aqua on 90% of it, and can't find anything I can fault. I'm still wondering how I've seen 1st hand letting the medium dry out a bit more, definitely does get the roots to go looking. But only seems beneficial in early veg while roots are establishing.
Hope it makes sense I've rambled on a bit