I have been riding an Extralite Ultrapush riser and Ultrastem for about four years on xc-type trails. I have never crashed (I don´t count falling off as crashing) and the bar has only suffered impacts from the bike falling over onto it´s side.
(I know, I know, the bike falling over onto a 135g bar is not a sensible thing bujt these things happen.)
I really would like to know if there is a general consensus of opinion about the safe-life of a lightweight bar, especially now that carbon parts have been around for so long.

I had an easton monkeylite xc carbon bar bought almost second hand in 2000 and have only just retired it, so I reckon you should be fine. If it worries you though bin it and get something a bit heavier, you can’t put a price on peace of mind

Gareth