The Collaborative International Dictionary of English v.0.48:

Enduring \En*dur"ing\, a.
   Lasting; durable; long-suffering; as, an enduring
   disposition. "A better and enduring substance." --Heb. x. 34.
   -- En*dur"ing*ly, adv. --T. Arnold. -- En*dur"ing*ness,
   n.

WordNet (r) 3.0 (2006):

enduringness
    n 1: permanence by virtue of the power to resist stress or
         force; "they advertised the durability of their products"
         [syn: lastingness, durability, enduringness,
         strength]