khuon

If anything, carbon has a much higher fatigue life than metals. Barring scratches and high-speed impact/crashes, a carbon bar that's inspected often for signs of cracks and/or delamination should last as long as a bar of any other material. I've got a 5 year-old Easton CT2 flatbar on my MTB that's seen plenty of crashes and it shows no sign of trauma. One trick I use to check my CF components and frames is to establish some probe points and use a very sensitive ohmeter to check the resistance across multiple points. I keep track of these and if there's a change, I inspect the area for damage. CF will change resistivity when fibres break. This of course isn't a foolproof method but it can be used as a quick sentinel to trigger more thorough examination. Also, cleaning CF is always a good idea to make it easier to detect damage. Note that you can't probe directly on the surface of most CF, you need to do it at the edges. Actually I use metal inserted parts (dropouts, BB shell insert, seat-tube insert, head-tube insert, water-bottle mount holes, etc) as my measurement points for the frame. For the bars, I take off handlebar plugs and go end-to-end.