To my mind this line of reasoning is exaggerated and uncompelling, perhaps even immoral, insofar as it fails to take into consideration the ambiguities of life and serious problems afflicting theism. It hoists far too much responsibility upon people, given the fact that the circumstances of life in which the choice has to be made do not make the choice correspondingly clear.
Imagine someone forces you into a dense fog, and you can barely make out the line of a fork in the road in front of you. You have to choose one way or the other; he obliges you. Now one of the road seems more appealing to you than the other: it is a bit more stable, it seems as if it is easier to walk upon than the other, and it looks more regularly traveled than the other. Then appears someone who tells you, If you go down that road to the left, nice as it looks, you will fall down a never-ending cliff, and it will be constant torture for you all the way down; it may never end. But if you go down this path to the right, you will have to make some serious changes to your way of walking which will be painful, but you will end up in a nice place where you will enjoy your stay forever. But on the other side appear other persons who negate what the first person told you, and some of their arguments seem persuasive.
Is it not obvious in a situation like this that the choice is exaggeratedly momentous? The evidence at hand is not sufficiently clear to warrant the choice's being so critical; it is unfair for you to be put in a situation in which so much is at stake against your will. But this choice is not even analogous to the choice the free will defenders of hell think we have to make, because our experience of life is even more troubled than this.
It also calls into question God's goodness. Imagine placing a child on the edge of a cliff and demanding that he learn to walk there. More than that, there are some toys or some otherwise attractive things hanging just off the edge of the cliff, so that he is pulled in that direction all the time by what he sees. Wouldn't that be insane? Wouldn't that be outrageous? But then why wouldn't it call into question God's goodness for calling upon us to make such a choice between eternal hell or heaven in analogous conditions?
Take a moment and think over the heinous and grave evils which occur in the world -- cold-blooded murders; rape and sex slavery; kidnapping and child-snatching; war, racism, and genocide; natural disasters that happen at random and leave the unprepared in ravaged conditions; disease and forces of nature which overpower a human easily. Think of Lizaveta in Dostoevsky's Crime and Punishment who walks into her own home at the wrong moment and is murdered brutally because Raskolnikov can't allow any witnesses. Think of the children being impaled and killed by dogs in his The Brothers Karamazov. Think of the way in which animals live in the wilderness, struggling to survive, regularly being eaten alive by stronger predators at random, and then think about the fact that this is the way it's been in nature for as long as anyone knows. The confrontation with pure evil calls into question the meaningfulness of life, its direction and teleology, and consequently the existence of God.
In light of all this, it seems to me simply not reasonable that a choice made in such ambiguous circumstances have eternal significance. If that is what it takes for freedom to be robust and meaningful, then perhaps we don't live in a world in which such freedom is worth having.
In any case, however, it's not obvious that we actually think like that. If I may not go to jail forever for committing some crime, and its consequences may not be eternal in the sense that they go on as long as I do, but it doesn't follow that my choice to follow the law is not meaningful or motivated. It doesn't follow that if I do break the law, it's no big deal since the consequences will eventually pass. No one actually thinks like this. Even Christ knew he would be resurrected and the pain of the cross would pass, but this doesn't make his anguished tears in Gethsemane irrational or unmotivated.
To me, then, it seems that this defenders of a robust conception of freedom of the will, who also wish to defend the "traditional" doctrine of hell with it, are being unreasonable. They are hoisting too much importance on this life; they are making this life more important than it can be, given its ambiguous and questionable nature.
This doesn't take out the urgency of the call to Christ. There is a hell and it is hellish, even if it doesn't go on forever. I am just opposed to the outrageous disproportion between a decision made in seventy years of life and unending consequences for the wrong choice made. If hell were ten million years long and that's it, that seems to me enough to warrant making a determined choice now and not later. It doesn't have to last forever.