Un*fail"ing*ness

from The Collaborative International Dictionary of English v.0.48

Unfailing \Un*fail"ing\, a.
   Not failing; not liable to fail; inexhaustible; certain;
   sure. --Dryden. -- {Un*fail"ing*ly}, adv. --
   {Un*fail"ing*ness}, n.
   [1913 Webster]