Source : Webster's Revised Unabridged Dictionary (1913)

Staleness \Stale"ness\, n.
   The quality or state of being stale.

Source : WordNet®

staleness
     n 1: unoriginality as a result of being dull and hackneyed [syn:
          {triteness}]
     2: having lost purity and freshness as a consequence of aging
        [ant: {freshness}]