I have grown plants to be quite rootbound in these things and the roots did not start to die: the plants just grew more slowly.
I have used that exact strategy that you describe and that is a good option. You can also pot up to a larger planter if you want to keep growing the plant larger.
I have used that exact strategy that you describe and that is a good option. You can also pot up to a larger planter if you want to keep growing the plant larger.