I may get flamed for saying this but if a carbon frame is well designed and constructed, it will out last the owner unless it is wrecked.

However, a lot of bike manufacturers were relatively new to carbon and might not have had a lot of experience building with it. I think Trek was one of the early adopters though. If the frame looked like it was in good shape, I would be OK with it. Most likely it will have a 1" head tube if that matters to you.