Eonian is the more scriptural word. Here are resources that show why eonian is the better literal translation.

• Eternal or Eonian? Part One (Introduction; A Common Argument Refuted) by Aaron Welch
• Eternal or Eonian? Part Two (The Hebrew Word Olam) by Aaron Welch
• Eternal or Eonian? Part Three (The Olam God) by Aaron Welch
• Eternal or Eonian? Part Four (The Greek Noun Aión) by Aaron Welch
• Eternal or Eonian? Part Five (The Greek Adjective Aiónios) by Aaron Welch
• Eternal or Eonian? Part Six (The Eonian God; The Kingdom of God; Eonian Life) by Aaron Welch
• Eternal or Eonian? Part Seven (Then Comes the End; God All in All) by Aaron Welch
• How long does “for ever” last in the Bible? by Drew Costen
• EONIAN Eternal or Age-lasting? by A. E. Knoch
• THE GREEK WORD AION—AIONIOS, TRANSLATED IN THE HOLY BIBLE, SHOWN TO DENOTE LIMITED DURATION. by Rev. John Wesley Hanson, A.M.
• MF: 42: Everlasting Hell??? by DCTime