Dear Jim:
There is an “urban myth” that Body Armor “expires” after the official manufacturer warranty runs out. Actually, the standard five year warranty is simply based on the insurance companies legal need to limit their liability – not on the actual performance of armor. (I have a sneaking suspicion that manufacturers don’t complain too much about being able to sell new Body Armor every five years either!)
The National Institute of Justice (NIJ) has found that 10 year old used armor tests as good as new. Since we deal with a lot of Police Surplus we run tests on the oldest and worst looking vests we see (vests we would never sell because they are over 25 years old, on the old NIJ 0101.02 standard). Oddly enough, these old and beat-up vests always stop 9mm +P FMJ and .357 Magnum +P JSP for us.
Here is a direct link to data and photos.
Of course decertified Zylon vests are not to be trusted – regardless of age. However, good Body Armor lasts much, much longer than the five year warranty/insurance policy.
Thanks, – Nick, BulletProofME.com Body Armor