There will be no end to the life of the Hereafter
Question

Will humans live in the after-life forever or for only as long as Allah wishes ? What is the Islamic belief regarding this ?
Praise be to Allah.Allaah has decreed that this world will come to an end, and He has decreed that its people will die. Allaah says (interpretation of the meaning): 
“Whatsoever is on it (the earth) will perish.
And the Face of your Lord full of Majesty and Honour will remain forever” [al-Rahmaan 55:26-27]
 “Everyone shall taste death. Then unto Us you shall be returned” [al-‘Ankaboot 29:57]
Then Allaah will resurrect His slaves and give them eternal life to which there will be no end. He will bring them to account for their deeds, and He will reward those who did good deeds and punish those who did evil deeds. Mankind will be divided into two groups, one in Paradise and one in Hell. The people of Paradise will abide therein forever, and the kaafir people of Hell will abide therein forever also.
 There are many verses and ahaadeeth which clearly state that, for example: 
1 – Allaah says (interpretation of the meaning): 
“But those who believe (in the Oneness of Allaah — Islamic Monotheism) and do deeds of righteousness, We shall admit them to Gardens under which rivers flow (Paradise), abiding therein forever. Therein they shall have Azwaajun Mutahharatun (purified mates or wives), and We shall admit them to shades wide and ever deepening (Paradise)” [al-Nisa’ 4:57]
Al-Tabari said: 
“abiding therein forever” means, they will stay there forever, and it will never end or cease; they will remain there forever. Tafseer al-Tabari, 5/144 
2 – Allaah says (interpretation of the meaning): 
“Allaah will say: This is a Day on which the truthful will profit from their truth: theirs are Gardens under which rivers flow (in Paradise) — they shall abide therein forever. Allaah is pleased with them and they with Him. That is the great success (Paradise)” [al-Maa'idah 5:119]
3 – Allaah says (interpretation of the meaning): 
“Verily, those who disbelieve and did wrong; Allaah will not forgive them, nor will He guide them to any way.
Except the way of Hell, to dwell therein forever; and this is ever easy for Allaah” [al-Nisa’ 4:169]
4 – Allaah says (interpretation of the meaning): 
“Verily, Allaah has cursed the disbelievers, and has prepared for them a flaming Fire (Hell).
Wherein they will abide for ever, and they will find neither a Wali (a protector) nor a helper” [al-Ahzaab 33:64-65]
5 – Allaah says (interpretation of the meaning): 
“(Mine is) but conveyance (of the truth) from Allaah and His Messages (of Islamic Monotheism), and whosoever disobeys Allaah and His Messenger, then verily, for him is the fire of Hell, he shall dwell therein forever” [al-Jinn 72:23]
Ibn Katheer said:  
“he shall dwell therein forever” means, he will stay there and remain there, he will have no way out of it and that will never cease for him. Tafseer Ibn Katheer, 3/520 
6 – Allaah tells us that the kuffaar will not die in Hell and they will never have a good life. Allaah says (interpretation of the meaning): 
“Verily, whoever comes to his Lord as a Mujrim (criminal, polytheist, sinner, disbeliever in the Oneness of Allaah and His Messengers), then surely, for him is Hell, wherein he will neither die nor live” [Ta-Ha 20:74] 
“There he will neither die (to be in rest) nor live (a good living)” [al-A’laa 87:13]
al-Qurtubi said: 
“There he will neither die (to be in rest) nor live (a good living)” means, he will never die so as to find a respite from the torment, and he will not live a life that will be any good. Tafseer al-Tabari, 20/21 
7 – It was narrated that Abu Sa’eed al-Khudri (may Allaah be pleased with him) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Death will be brought forth in the form of a black and white speckled ram, and a caller will cry out, ‘O people of Paradise!’ They will crane their necks and look, and he will say, ‘Do you recognize this?’ They will say, ‘Yes, it is death,’ and all of them will have seen it. Then he will cry out, ‘O people of Hell!’ They will crane their necks and look, and he will say, ‘Do you recognize this?’ They will say, ‘Yes, it is death,’ and all of them will have seen it. Then the ram will be slaughtered, and he (the caller) will say, ‘O people of Paradise, it is eternal and there will be no death; O people of Hell, it is eternal and there will be no death.’” Then he recited (interpretation of the meaning): “And warn them (O Muhammad) of the Day of grief and regrets, when the case has been decided, while (now) they are in a state of carelessness, and they believe not” [Maryam 19:39] Narrated by al-Bukhaari, 4453; Muslim, 2849 
According to the version narrated from Ibn ‘Umar in Muslim (2850): “And the joy of the people of Paradise will be increased, and the grief of the people of Hell will be increased.” 
Ibn al-Qayyim said: 
This ram and the action of laying it down and slaughtering it whilst the two groups are looking on is something real; it is not something illusionary or symbolic, as some people made the serious mistake of suggesting. They said that it is a description, but a description cannot take a physical shape, let alone be slaughtered. 
That view is not correct, for Allaah will cause death to appear in the form of a ram which will be slaughtered, just as He will cause deeds to appear in visible forms by which people will be rewarded or punished. Allaah can cause descriptions to appear in physical forms the substance of which is the description, and He can create characteristics from physical beings, and He can create descriptions from descriptions and physical beings from physical beings. All four categories are possible for Allaah, and there is no contradiction in any of that. It is not something impossible, and there is no need for far-fetched interpretations such as saying that it refers to the slaughter of the Angel of Death. All of that is a misinterpretation of the words of Allaah and His Messenger and a false understanding that is not dictated by reason or the reports, which is caused by lack of understanding of what the Messenger said. 
Haadi al-Arwaah, p. 283, 284 
8 – It was narrated from Ibn ‘Umar (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) said: “The people of Paradise will enter Paradise and the people of Hell will enter Hell, then a caller will stand between them and will say, “O people of Hell, there is no death; O people of Paradise, there is no death. It is eternal.” (Narrated by al-Bukhaari, 6178; Muslim, 2850) 
9 – It was narrated from Abu Sa’eed al-Khudri and Abu Hurayrah that the Prophet (peace and blessings of Allaah be upon him) said: “A caller will cry out (i.e., to the people of Paradise): ‘You will be healthy and will never fall sick; you will live and will never die; you will remain young and will never grow old; you will feel ease and will never be miserable.’ This is what Allaah says (interpretation of the meaning): ‘And it will be cried out to them: “This is the Paradise which you have inherited for what you used to do”’ [al-A’raaf 7:43].  
Narrated by Muslim, 2827 
So hasten to do righteous deeds in this world, for it is only a short time before you will move to the realm of eternity, either to Paradise whose delights will never end or to Hell whose heat is eternal… so hasten and beware of procrastinating, for most of the pain of the people of Hell will be because of procrastination. 
May Allaah make us and you among the people of Paradise. Ameen.