I would guess that the main issue is that the sensor contacts corrode with time, so that in an impact, the sensors may not not make complete electrical contact, which potentially results in delayed deployment, or none at all.

Random deployment would indicate a defect due to a faulty system, not an aged one.

So I would rest easy that you won't just be driving along one minute and the next minute, your eating an air bag...

__________________
2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car