I had this issue recently come up in a supply closet at a new work
site where the former repairer had stockpiles of now "new old stock".
I suggested that everything over six months old should go, unless it
could be turned into packing leather.

Grant Chapman
West Point, New York

 [ I found this description when I searched for "packing leather":
 [
 [ "Leather is tough, pliable, and wear resistant. Leather is unaffected
 [ by cold, enabling it to withstand high pressure at low temperature,
 [ and its low coefficient of friction means it generates less heat, and
 [ lasts longer as a result. Leather is impregnated with greases, oils,
 [ waxes, synthetic resins, or synthetic rubber as required for various
 [ applications -- thus leather seals are impermeable to hydraulic
 [ fluids and air. Further, leather is far more cost effective than
 [ synthetics." Source: http://cwmarsh.com/why-leather/ 
 [
 [ -- Robbie