Board Thread:Lore Discussion/@comment-142.167.98.9-20130810075540/@comment-15110880-20130810193919

Well, depending on your stands on the whole Tiber Septim issue, becoming a Divine is a way to become immortal - sort of.

Daedra are also immortal, so somehow becoming a daedra would allow you to live forever. (End of the Shivering Isle main quest for example)

Time line considered, Miraak should be well over a thousand years old, and he's just a nord. The Dragonblood might have prolonged his life, allowing him to live for thousands of years (lived since the Merethic Era), or it might be that Hermaeus Mora has somehow kept him from aging. So daedra intervention and/or Dragonblood might be acceptable means.