From change + -less.

changeless (not comparable)

1. unchanging

   Synonyms: Thesaurus:changeless

   • 1905, Lord Dunsany [i.e., Edward Plunkett, 18th Baron of Dunsany], The Gods of Pegāna, London: [Charles] Elkin Mathews, […], →OCLC ↗, page 23 ↗:

     Lest men grow weary down on the great Worlds through gazing always at a changeless sky I will paint my pictures in the sky. And I will paint them twice in every day for so long as days shall be.