I have read in several places that the carbon fiber has a shorter life span than the alluminium, and i was wondering just what would it be. I am not referring to accident related failures of the frame. I would like to know how much would a frame hold for a road bike if i didn't have any accidents and road it almost daily for lets say 10 miles.
Absent some kind of abuse or extraordinary stress (like falling on top of the bike while it's lying on the ground - stressing the tubes from the side, riding with a friend sitting on the top tube...) a carbon fiber frame should outlast the rider.
For carbon forks in general, there should not be any limited life span, as carbon composites themselves are not subject to fatigue failures as metals are. So the fatigue life of a properly made carbon composite is 'infinite'.
There is no limitation because carbon has a natural flexibility. It can be used a hundred years while maintaining the same stiffness.
The good news is the fatigue life of carbon fiber is immensely more than that of metals. While the writer expresses concern about his carbon fork lasting as long as a metal component, there is nothing to worry about in terms of fatigue life on a composite fork.