if you can show me a case where both lines on both gears ( total of 4 lines) have failed at the same time due to fatigue etc.
Oops, RTFQ Bill - I didn't see the 'both sides' thing sorry.
Yes, I have never heard of all brakes failing. I've had them fail completely on one truck due to a couple of wheels coming apart, and another company 747 went off the end of the runway in the Middle East on takeoff for the same reason.