Haven't done a valve check on my current '18 (MBD!) so still has stock CCT. On my previous '12, I installed a Graves unit at first check and didn't touch it until I flipped it for the too-good-to-pass-up '18. That was at ~42k total miles with ~18k on the Graves...still quiet. My '18 is close to check time so I'm pretty sure a Graves is in my future. The difference in noise (at least on my '12) was significant.
~G