When people speak of "eternity" I suspect they mean beyond space/time - i.e. counting is irrelevant.
But when we speak of God the Creator of space, time, energy, causality, autonomy etc. - the term "timeless" is more appropriate since such created things are not properties of - or restrictions on - the Creator of them.
So...... eternity is NOT Possible.?..
because if eternity future is possible eternity PAST must also be possible..
AND if eternity past is possible... there might not have been a beginning..
There are ramifications to everything.. that is to say.. "EXPANDING" might be the "wrong word" for whats goin' on..
Maybe; revolving, speeding up, dimension shift, or "something else"...