Is Eternity just Everlastingness?

Eternity must imply everlasting time,

but

although the Greek words aidios and aion naturally mean everlasting, there was a long tradition, from Philo onwards, of distinguishing eternity from everlastingness, or sempiternity as it was sometimes called.
Eternity is not untime, but all time, not timelessness, but time not subject to the limitations of our mortal existence.
The contrast is not a logical one, but an evaluative one

Aeternitas igitur est interminabilis vitae tota simul et perfecta possessio

perfecta possessio
interminabilis vitae
The vulnerability of God

and

the boringness of man