The Collaborative International Dictionary of English v.0.48:

Changeless \Change"less\, a.
   That can not be changed; constant; as, a changeless purpose.
   -- Change"less*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

changeless
    adj 1: not subject or susceptible to change or variation in form
           or quality or nature; "the view of that time was that all
           species were immutable, created by God" [syn:
           immutable, changeless] [ant: changeable, mutable]
    2: unvarying in nature; "maintained a constant temperature";
       "principles of unvarying validity" [syn: changeless,
       constant, invariant, unvarying]
    3: remaining the same for indefinitely long times [syn:
       changeless, unalterable]

Moby Thesaurus II by Grady Ward, 1.0:

104 Moby Thesaurus words for "changeless":
   abiding, all-knowing, all-powerful, all-seeing, all-wise, almighty,
   boundless, constant, continuing, creating, creative, durable,
   enduring, eternal, eternally the same, everlasting, firm, fixed,
   frozen, glorious, good, hallowed, highest, holy, immobile,
   immortal, immutable, incommutable, inconvertible, indefeasible,
   inert, inevitable, infinite, insusceptible of change, intact,
   intransmutable, invariable, inviolate, irretrievable, irreversible,
   irrevocable, just, lasting, limitless, loving, luminous, majestic,
   making, merciful, noble, nonreturnable, nonreversible, numinous,
   omnipotent, omnipresent, omniscient, one, permanent, perpetual,
   persistent, quiescent, radiant, remaining, reverseless, rigid,
   sacred, shaping, solid, sovereign, stable, static, stationary,
   staying, steadfast, supreme, sustained, timeless, torpid,
   ubiquitous, unalterable, unalterative, unaltered, unbounded,
   unchangeable, unchanged, unchanging, unchecked, undefined,
   undeflectable, undestroyed, undeviating, unfading, unfailing,
   uniform, unlimited, unmodifiable, unremitting, unrestorable,
   unreturnable, unshifting, unsusceptible, unvariable, unvaried,
   unvarying