I'm running the 17gal tubs outside and get 2, sometimes 3 runs, but never more, then a re-mix. Like you've experienced, by then it is littlr more than VC and perlite. I don't add worms per se, but do use a lot of fresh VC for top dress and they grow fasy enough from yhe cocoons in the VC. About 1/2 the time it just gets dumped on my raised beds that ARE no till and re-start with fresh mix. LOL, I mean, when it's full of perlite and still like mud it's time to spread it out somewhere else.
I have 12, 20 gallons and a 40 gallon tote outside where i keep extra soil. I put my clones in 2 gallons from the outside tote and then remove 2 gallons from the 20s and that goes into the tote outside. I added tons of worms and now worms are in every inch of soil, even the stuff outside in the tote. When i start a new clone i add nothing to the soil. Straight from the tote to the pot and my clones love it. Before i add another plant into a 20g i top dress, transplant and water. My worm bin is looking like i can finally pull some fresh ewc amd use them. I wemt heavy on the rice hulls in my mix becuz i know over time adding all the extra stuff would make it compact but not this soil. Going heavy on the rices hulls really does the trick. Also my 20s are filling up crazy with mites and worms.