"The magnitude of the punishment matches the magnitude of the sin. Now a sin that is against God is infinite; the higher the person against whom it is committed, the graver the sin—it is more criminal to strike a head of state than a private citizen—and God is of infinite greatness. Therefore an infinite punishment is deserved for a sin committed against Him." - Thomas Aquinas (Summa Theologica, Ia2ae. 87, 4.)
This is sound logic. In our American culture today, we attempt to make all men equal to one another. But let's face it, if someone would commit an act of violence against an elected official which resulted in that individual's death, the punishment would be swift and severe, increasing proportionately to the rank held by the victim. If that same someone would commit that same act of violence against a motorist on the road, the proceedings would drag on for months, if not years, and the sentence levied upon the perpetrator would likely be mild in comparison.
If we extend this concept to the infinite, it only makes sense that an 'endless' punishment be meted out upon those of us who sin, all of us (Psalm 14:1-3, Psalm 53:1-3, Romans 3:10), in order for God's character trait of being JUST to be satisfied.
I for one am exceedingly grateful to Him for His gift!