With respect to Carbro, Mac McCowan can be a source of information. He's the only one I know of that claims to have made 3 color carbros recently. His website indicates that he currently only does monochrome, but that he has done 3 color work in the past.
Mac McCowan website
There is also an example of a 3 color carbro currently on our favorite auction site that has a good image of the vintage (1950's) carbro.
Vintage 3 color carbro
You can see there doesn't appear to be any fading or deterioration of the image. Carbro uses pigments to form the image which should not fade.