Hell is eternal. According to Matthew 25:46, Jesus said, "and these shall go away into everlasting punishment, but the righteous into life eternal". Romans 16:26, speaks of the everlasting God. Hebrews 9:14 refers to the eternal spirit.
There are four expressions in these three verses to be considered. They are "everlasting punishment", "eternal life", everlasting God", and "eternal spirit". The only difference between everlasting and eternal in our language is a difference in spelling. They mean the same thing. The Greek word translated as everlasting or eternal in these three passages is the same. It is "ionious" which means eternal, everlasting, without end, never to cease, or indeterminate as to duration.
There is another argument which can be made against the eternality of hell. which cannot be applied against the eternality of God the Father, God the Spirit, and Heaven. If one were to take the poisition that hell were to last only a thousand years, to be consistent he would also have to contend that the Father, Spirit and Heaven will last for only a thousand years. That is true for the same word used to describe the duration of Hell's punishment is also used to describe the duration of the Father, Spirit and Heaven.
The very moment that the disobedient cease to be punished, the righteous will cease to be blessed and the Father and Spirit will cease to exist. Hell's punishment will continue forever and ever.
Two arguments advanced against this position are as follows. First, some say that would make hell too long. They argue that it would not be right to punish one eternally for five years of disobedience. If that is true it would also be wrong to bless one eternally who had lived for only five years in obedience to God's will. If not, why not? The same arguments used to rid the Bible of the doctrine of hell, can be used with equal validity against the doctrine of heaven. Those who feel that eternal punishment is too long, reflect upon every system of justice in the world. How does one determine the enormity of an act? By the time it takes to perform it? or by the act itself? For example, in fifteen seconds, a man could kill a dozen people by throwing a hand grenade into a crowded store. If that were done, should the killer go to prison for only fifteen seconds? Should he be placed in the penitentiary for only sixty seconds? Would the demands of justice be satisfied if he served a jail sentence of two minutes? Oh, no, if he were able to escape execution, he would have to spend the rest of his life behind bars for an act which took only fifteen seconds to perform. The heinousness of evil is seen in the act itself, rather than by the time involved in its perpetration. The most horrible thing one can do is live in rebellion to the will of Almighty God. Those who live five years, five months, or five days in defiance of the Lord, and die in that condition will be punished in hell forever.
Second, there are those who believe the punishment of Matthew 25:46 means eternal annihilation. They maintain that the disobedient will be cast into the fires of hell and simply experience a cessation of all existence. When Revelations 21:8 speaks of a second death, they understand it to refer to a second physical death. In their view, when one dies the first time he goes back to where Adam was before he was created. Where was Adam before he was created? He was not. They believe that at the Lord's second coming, the dead will be re-created and those who have rejected the Saviour will be burned, experience a second physical death and be annihilated forever. Everlasting punishment to them means to be dead, like an animal, eternally.
In response to that position, consider the word translated as punishment in Matthew 25:46. It is, "colason", which means to chastise, or torment. In I John 4:18, it is translated as torment. Read Luke 16:19-31, and notice that four times the rich man in the flames of Hades is described as being in anguish or torment. See Revelations 14:11 and 20:10, where the word torment is used to describe the fate of the unsaved. If those who leave this world unprepared to meet God go into eternal nonexistence, how could the words torment or anguish be used to describe their state? Torment can exist where there is consciousness. It is impossible to torment a dead dog, since he is not conscious. There is a difference between a man and a dog. Man survives the grave and judgement. The unsaved shall go away into everlasting conscious, suffering torment. That is what Hell is like, If you are not a Christian, if you are a backslidden child of God, I plead with you to turn to Christ by obedience to his will and flee from the wrath to come. Please do not neglect your soul.