Why does the Creator punish His slaves with eternal torment for few sins committed during their short lives?

Many crimes lead those who commit them to life sentence. Does anyone object saying that this life sentence is unjust because the criminal committed his crime only in a few minutes? Is a ten-year sentence considered unfair because the criminal embezzled from the money only within one year? Penalties do not depend on the duration of committing crimes; rather, they depend on the magnitude and gravity of the crime itself.