People who ride carbon mountain bikes absolutely baffle me. The thing is going to get seriously chewed up if you're having fun and pushing your limits, why make it a glass canon to boot?!
Carbon MTBs are pretty strong. Just don't clamp the frame so much you are crushing it and avoid direct rock hits, which will damage any material anyway.
> avoid direct rock hits
Given that I mostly ride my local volcano, this may not be a practical constraint for me.