1) There may be a category fallacy involved in the claim, since time is a part of this universe whereas Heaven and Hell are not.
2) In our own imperfect judicial systems, there is almost never a direct link or correlation between the time involved in committing the crime and the duration of appropriate punishment.
3) A factor that does matter (even in our judicial systems) is the person or authority against whom the crime is committed. Where the issue is eternal punishment in Hell, the authority against whom the crime has been committed is the supreme Authority--the Creator of all things, the all-powerful, Holy God who gives life in the first place. He is also the only Authority who can (and does) offer a pardon.
4) The claim of unfairness seems to imply that what gets people condemned to Hell are little sins, the breaking of somewhat arbitrary rules that God set up to keep people from having fun. Actually, according to the Bible, what gets people sent to Hell is utter and wholesale rejection of their Creator and of His loving authority in their lives.
5) The claim also seems to assume that the person who so rejects God will wish--once he finds himself in Hell--that he could change his mind. I find no reason--and certainly no evidence in Scripture--that this is the case. Rejection or acceptance of God in this life is done with eyes wide open, and is a decision foundational to who we are. The person who hates God in this life will rather remain in Hell for eternity than choose to love and worship Him after death.
This brings us to the last point I want to make (though there are undoubtedly other problems with the claim that Hell is unfair). For this one, I want to address a particular form of the claim, directly quoted from an email I received:
Eternal punishment seems a bit harsh for any sins committed in only 70-odd years on this confusing planet, especially the sin of disbelief.This form surfaces two further, related misunderstandings shared by many who claim that the biblical doctrine of judgment is unfair.
In the first place, this claim mischaracterizes the crime as mere disbelief. This is not the Bible's portrayal. (Again, it's perfectly legitimate to allow the Bible to defend itself in this instance, since it is the biblical doctrine of Hell that is being argued against; it is the claimant who first brought the Bible into the discussion, not I.)
According to the Bible, eternal judgment comes because we reject our Creator and His authority over our lives, choosing instead to live according to our own inclinations (which choice leads to brokenness in all our relationships--with God, self, others, and creation), and then rejecting God's merciful, sacrificial offer of pardon. We hate God and run from Him, and Hell is simply the place reserved for those who want nothing to do with God.
Second, this claim depends upon pretending that there is insufficient evidence for believing in God. And while even we Christians sometimes act as though the evidence is worth quibbling about (with the professed atheist), the truth is far different.
According to the Bible (especially Romans 1:18-32), all men know there is a God. Further, the natural reaction of fallen humans is to suppress that knowledge, run from God, and delude ourselves into thinking we can pretend that He doesn't exist. In our day--where the fallacious rhetoric of the so-called New Atheists becomes best-selling books--we have an entire subculture of people who not only engage in such foolishness but communally approve and encourage such delusion in others.
To put it bluntly, the acquaintance who emailed me is not 'confused' about the evidence (as he claims); instead, he is in a state of open rebellion against God, which leads him to self-delusion about the evidence.
Throughout the history of human civilization--and certainly throughout western history for which we have the written records--as men have looked around them at the starry heavens, at other living things, at the planet on which they live, the logical conclusion to which they have come is that things are the way they are because they are designed. In our generation, the evidence available to us is exponentially greater than that available to previous generations. Our technology allows us to see the birth of gallaxies at the beginning of the universe some 13+ billion years ago. In the other direction (in terms of scale), we can now see the insides of cells and even of the molecules that make up cells. And as each scale of the universe becomes accessible to us, the overwhelming characteristic continues to be that of exquisite design, the evidence of an unimaginably powerful, wise, loving Designer behind it all.
In light of all this, the modern atheist/agnostic project is radically illogical. To see this exquisite design at every level and claim (as do Richard Dawkins, Francis Crick, and others in our day) that it is an illusion (only 'apparent') is absurd. To act as though the burden of proof ought to be on the people who (in keeping with the majority of people throughout history) see the design in the universe as real is bizarre. And to order one's life on the basis of this type of absurdity is mere self-delusion (of the type that Romans 1 describes).
The evidence for God is not confusing. The evidence for the careful design of this universe is not 50/50. The evidence for purpose and design is not even merely overwhelming. God's creation of this universe left no room for doubt. It is only our own stubborn, proud rejection of His authority in our lives that leads us to fool ourselves into thinking that we can feel justified in questioning His existence.