It is usually considered that life after death is eternal/ forever. Let us analyze this concept in the light of Quran.
Eternity is Allah’s Quality which is not shared by anything else, by any creation. This quality of ‘eternity’ may not be assigned to the Paradise and the Hell. The following Quranic verses make it clear that the Paradise and the Hell are not eternal entities.
“[They will be] abiding therein as long as the skies and the earth endure, except what your Lord should will. Indeed, your Lord is an effecter of what He intends” (hud-107).
“And as for those who were [destined to be] prosperous, they will be in Paradise, abiding therein as long as the skies and the earth endure, except what your Lord should will - a bestowal uninterrupted (hud-108).
Both above stated verses explain that the people consigned to the Paradise or to the Hell will be abiding therein as long as the skies and the earth exist but, if Allah wills it so, He may end Paradise life even before end of the skies and the earth. In other words, the Paradise is not eternal entity.
The word 'abadan' repeatedly used in Quran regarding the Paradise and the Hellish life does not mean 'eternal'. Actually the word ‘abadan’ is used in Quran to describe uninterrupted state/situation; this word, in Quranic terminology, carries with it a sense of continuity, without interruption. In other words when this word ‘abadan’ is used to describe Paradise life or Hellish life, it means as long as man will remain in the Paradise or in the Hell, that state of being in the Paradise or in the Hell will be continuous, not interrupted by any pain or pleasure respectively. This word ‘abadan’ does not mean ‘eternally’; this fact is also evident from the following verse.
"And do not pray –ever/ ‘abadan’- [the funeral prayer, Muhamma(saw)] over any of them who has died or stand at his grave. Indeed, they disbelieved in Allah and His Messenger and died while they were defiantly disobedient" (taubah-84).
If we take the word 'abadan' as meaning 'eternally', it would mean our Nabi (saw) is being forbidden from standing at grave of disbelievers even in life after death. But there is no point in forbidding our Nabi (saww) from standing at the grave of disbelievers in the life after death; because there is no death and no grave in the Hell or Paradise after death. Actually 'abadan' means 'ever/continuously'; in other words, our Nabi (saw) is being forbidden to pray for and stand at the graves of disbelievers, and the word ‘abadan’ emphasizes that our Nabi (saw) should avoid such a practice continuously/ uninterruptedly.
We may conclude that the Paradise and the Hell are not eternal entities; eternity is a quality to be assigned only to Allah; no creation can be assigned this quality. The Paradise and the Hell will be discontinued, when the skies and the earth will be destroyed to be reproduced (for details plz see my article ‘Origin of Universe and Dark Matter’.