Do Xenons fade away...
 

or do they burn out with most of their original brightness? Just wondering if I should pro-actively replace them at some point.

when they turn pink, that's when you replace them :thumbup:

From what I heard and read, they also might get slow to light up when switched on.

...or if they blinking few times before turning on...

Xenon lights use a gas vapor arc instead of a conventional wire filament. The arc is maintained by a very high voltage of 700 volts. Xenon lights are very long lived and not known to deteriorate over their life.

Covered. http://www.xoutpost.com/lounge/33505-...light=bi-xenon

REPLACED BOTH OF MY HEAD LAMPS
 

MY WIFE HIT A DEER WITH MY X5 AND WHEN THE FRONT END WORK WAS DONE, I HAD THEM REPLACE BOTH OF MY HEAD LIGHTS. AND LAST NIGHT WAS THE FIRST DRIVE AT NIGHT SINCE I GOT MY X BACK, AND THE HOLE DAWM ROAD WAS LITE UP, WOW, WHAT A BIG DIFERANCE.

I JUST LOVE MY X5;)