I'll probably catch some flack, but I have been growing in 3 gal
smart pots using the same soil for a year now. Recycling/vermicomposting and using aacts is honestly the biggest factor for me. While I do absolutely agree that the more soil mass, the easier it will be and it may be a happier system, but for me that wasn't an option when planning my grow. I wanted to rock something with a quicker turn over rate and I love perpetual so I married the ideas of living soil and perpetual by using worm bins. I have two worm bins set up. Whenever a plant finishes, I chop, topdress with whatever comes out of the bottom of the worm bin(castings/compost/humus ), some cover crop and water it for a week. After a week , the old stalk comes out easily with almost no root mass attached and it goes into the worm bin. Then I put a clone in it's pot and and keep rockin!! Everything gets aact once a month along with some bio media pro by better organix. Some may disagree with it even being possible in 3 gallons, but it's very obvious to me that I have a flourishing microherd because I am able to feed water and humic acid all the way through with no deficiencies and pull 1-2oz/plant(strain dependant) harvesting 3 plants every three weeks under ~600 true Watts led.
Forgot to mention that while I'm scooping from one worm bin, the other sits and collects scraps/paper for 4-6 weeks at a time so the worms aren't constantly being thrown around in both bins and allows time for castings to build up.