My Giant CFR1 (carbon tubing) which is basically the same as the Cadex botto mentioned, was going great until I got hit by a motor bike last year. Even then the carbon appeared unaffected, but the alluminium crown cracked. It was purchased in 1995.
I've seen two rear dropouts snapped on older Cannondales (maybe 16 year old frames). To be honest I don't know the background of their failures, but I'd guess it was due to an accident.