I think it is more of an issue of the life expectancy of the rubber bellows more than the carbon ring itself. From what I understand the rubber bellows essentially act as a spring seal that compresses the carbon seal tight against the stainless steel clip. Over time, the rubber bellows gets weak and looses its elasticity (as all rubber does) and it cannot compress the carbon ring and stainless steel clip as tight as it should be; therefore you now get air intrusion under heavy acceleration and cavitation.
I have heard that a good test for a carbon ring problem is to put a few plastic wire ties around the bellows to compress it and create a tighter seal between the carbon ring and stainless clip. You can also glob some Vaseline around the seal of the carbon ring and stainless clip. It will temporarily plug any air gap that might be causing your cavitation. After performing these temporary tricks, if your cavitation is gone then you need to replace your drive shaft seals.
I have also heard that the drive shaft must be perfectly aligned, as any misalignment will cause the wear ring to wear unevenly causing air gaps and cavitation eventually.
