Carbon tube frames from the '90s didn't fair so well because of epoxy
failures at the lugs. Technology transfer from golf, fishing poles, and
of course aerospace has changed the methodology dramatically so
contemporary frames will likely be longer lived than aluminum frames.
Should have a better idea in 5-10 years as the current surge in CF
frames begin to age out.
There is the difference between the material used and specific frames that use Carbon. Carbon has tremendous ability to take load cycles. The wear risk is more related to:
Crash damage or other nicks and nocks. New and still untested structures and fitting; Pressure to fully use the capabilities of the material and stretching it beyond comon sense; failure of aluminum components the material is bonded to, stuff like aluminum studs for brakes or stearing tubes. Eventually all these points should be worked out and it should become know for outstanding durabilty where desired.