I had about ten hrs (flying) on mine when I decided to strip it to change bearings and noticed the ends of the vapour tubes burnt, I was told they were only stainless (but probably a low grade of material that they use now), so I ordered the new CC and it is not showing any signs of the tubes being burnt now with 15 plus hrs so obviously better than what I had before.

I recently rebuilt a wren 54 at 28hrs it also had the ends of the tubes burnt but not enough I thought to warrant changing it for now.
There was one needle not working properly and two others partially blocked, (felix very kindly sent me a new needle which I replaced) my JJ1400 also had a couple of needles not working properly so I am wondering, if the other jets were working harder (hotter) which may have contributed to the burnt ends?