Until it develops into a thicker diamond hard carbon porcelain layer that a blade can't cut.
I've not noticed one way or the other.
I don’t get how it’s developing into a thicker layer, if the pipe’s chambers are wiped out after every smoke.
I’ve never had a need for any tools. I always wipe the chambers right after smoking, or the following day.
When it’s the following day, and it has more gunk inside, I’ll put a drop of water on a finger, and run it around inside the chambers and it actually does several things I’ve noticed. Makes it easier to pick out any leftover tobacco bits buried in the carbon, as it makes it softer to work with, helps to smoothen it, thin it out and even it out.