Why hasn't the curse died away in "The Rime of the Ancient Mariner"?

The curse cannot die, because the Mariner must retell his story in an attempt to teach others about the dangers of impulsive sinning.  When the Mariner sinned, it was on impulse and for his benefit--his motives were purely selfish.  Thus, his chance for salvation was destroyed, dooming him to an eternal living death.  His soul can never be free from its sin.  However, each time he retells his story to an attentive listener, he comes one step closer to the atonement needed for true salvation.  The ultimate question Coleridge leaves us is whether that atonement can ever truly be performed.