It's by no means necessary to use Carbon all the time - most people use it temporarily to remove tanins coming from a new piece of drift wood, or to remove medicine/chemicals after treatment. Once they reached their goal, they stop using it.
So there's no reason to be worried about stopping with using Carbon: just be sure you have enough biomedia for all the necessary bacteria, so the tank won't go through a (mini-) cycle.
So there's no reason to be worried about stopping with using Carbon: just be sure you have enough biomedia for all the necessary bacteria, so the tank won't go through a (mini-) cycle.