Eternity is not just a timeless zone, eternity is a person. When GOD created the first man, he gave man Dominion over things that was subject to time but his authority was limited to the visible realm subject to time(Gen : 1 vs 28 – 29). The invisible being subjected to time was outside the reach of his(Adam) authority, because the software that would have made his authority over invisible being authorized was missing, and that software is ZOE (Eternal Life)
Due to the lack of this life, the authority of man was restricted to the visible things in time despite he has been given the authority over all things subject to time ( visible & invisible ). That’s why when the devil look away the dominiary authority from man, devil was able to Lord over everything in time ( visible and invisible) because he is a spirit being. Though the devil didn’t have Zoe but he was an invisible being subjected to time, so when he collected the authority over things in time, he started dominating from the invisible realm.
The funny part of this misconception is that GOD never judged the invisible realm, neither did he judge man, he only oder cursed the ground to be hard for man to bring forth things that can sustain him, which he (GOD) reversed in the days of Noah, after the Earth was wiped out with flood. So man gained back his authority in time but was just limited to the visible realm( Gen. : 9 vs 3 ). Even when man fell, man was still in the image of GOD. GOD still saw man in his image even till CHRIST came. (Gen : 9 vs 4 – 6 ).
The spirit itself is subject to time. Demons and Angels are all subject to time, because everything created is subject to time. Eternity is a timeless zone, which means even Angels are not in eternity, demons are not in eternity, no celestial being exist in eternity. The devil himself is so much subject to time.