The Collaborative International Dictionary of English v.0.48:

Perdurance \Per*dur"ance\ (p[~e]r*d[=u]r"ans), Perduration
\Per`du*ra"tion\ (p[~e]r`d[-u]*r[=a]"sh[u^]n), n.
   Long continuance. [Archaic]
   [1913 Webster]