Dunno, never considered that. I mean, I'm 60kg. I can't see myself breaking a post unless it was utterly messed up before I bought it, which would hopefully be self evident.
The crabon posts I've bought from LFGSS have been unused anyhoo. Or so the sellers said.
especially a seat-post, @Howard, losing teeth is one thing, but castration by carbon is an eye-wateringly wince inducing proposition