The Collaborative International Dictionary of English v.0.48:

Lifetime \Life"time`\ (l[imac]f"t[imac]m`), n.
   The time that life continues.
   [1913 Webster]

WordNet (r) 3.0 (2006):

life-time
    n 1: the period during which something is functional (as between
         birth and death); "the battery had a short life"; "he lived
         a long and happy life" [syn: life, lifetime, life-
         time, lifespan]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "lifetime":
   age, animal spirits, animate existence, animation, being alive,
   birth, existence, for life, generation, having life, immortality,
   life, lifelong, liveliness, livelong, living, long life, longevity,
   period of existence, spriteliness, viability, vitality, vivacity