all rootbound actually means is your pots will hold less nutes and dry out quicker . if you dont want to repot just water your plants the same amount as normal but split it to 2 or 3 times a day instead of once a day ......
if you feed hydroponically.
if you are like me, and use just an amended soil, well then you're fucked.
BUT I never use anything less than a 5 gal on trained plants, or 3s if they are not trained and cloned.
my favorite is to use a 15 gal smartpot and put four of the same clones in there, train to a corner, and you can get 8 big ass colas in one 15 gal.
Recently I've been toying with going to just 3 gals, and top them to get me four colas, normally I LST to get a six pack of each plant but it's taking too much time.
Flipped quicker and I can squeeze in a whole extra harvest per yr