This may be sufficient to answer your question.
Middle English eternite, from Old French, from Latin aeternitās, from aeternus, eternal. Meaning time without end.
immortals have an eternity life
The word eternally is an adverb. It means to do something for eternity.
Forever everlasting
Eternal History The Making of From Here to Eternity - 2013 was released on: USA: 1 October 2013
Apeirophobia
Your question contains your answer.... "Eternity," implies without end. -Forever, or infinity can be used in conjunction with "eternity"
Hmmmm
The word 'eternity' appears four (4) times in the KJV Bible.
No, the word 'eternal' is an adjective, a word used to describe a noun.The noun form of the adjective 'eternal' is eternalness.A related noun form is eternity.
I think the word you want is "eternity".
eternity
One Second from Eternity The History of the Land Speed Record - 1971 V is rated/received certificates of: USA:G