The thing is though that your average CF component tends to be engineered for weight advantages and are generally less tolerant to abuse than say the average alu bar.
Most CF bars carry a stem tightening max torque of just 4-5Nm and a control torque of just 2Nm which unless you use a torque wrench or have magically calibrated hands is easy to over tighten for your average user. Alu bars by comparison are generally accepted to be “heavier” and made/ marketed for value and strength so are engineered to be more tolerant to ham fisted fitting/ crashing/ etc and not chase super light weight targets as a CF bar might be. It isn’t just the material but the intended use of a CF vs Alu bar (of course there are some exceptions and I am generalising to a degree but you get the point).
At the end of the day would you really take the risk that the previous owner has never over torqued the stem bolts or controls or that the bars have never taken a spill? This could apply to bars of any material but given the generally lower max torques for the average CF bar it isn’t unreasonable to suggest CF carries a slight increased risk on top of all of that.
And yes, I have damaged CF bars (Raceface and FSA) in fairly innocuous crashes and my GF bent an Easton EA70 in a crash so everything is possible in all materials 😀 I’d just rather know the history of the bar and the (ab)use it has been through by owning it for 4 years myself rather than go on the word of someone else. No reason a CF bar can’t last for 10 years if looked after!
