pot size question

[stinkyattic]

And the rule for pot size is a gallon for every month the plant is old.
...,.
According to Jorge Cervantes.... that's the rule.

Yeah, consider the source. :wtf:
That's a terrible rule, since plants grow at different rates depending on strain, lighting, stresses, ferts, etc.
One gallon per foot of main stem allows adequate root mass to support the foliage.
To transplant a large plant with minimal damage, allow the soil to dry out pretty badly, so it kinda shrinks up a bit. Then you should be able to slide the whole root ball out of the pot without the added weight of the moisture causing it to crumble under its own weight. Those plants can stay in those pots a little longer- wait until you are ready to go to 12/12 and go up to a larger pot, or start flowering now and watch for signs that they are getting root-bound. It is also easier to transplant a slightly root-bound plant, as the roots support each other and the soil during the switch.