Alternatives to "immortality"?

If you're not omniscient, you don't know that you're immortal.

If you're not omnipotent, then something could kill you.

Therefore, to become immortal, you must first become God.

Becoming God seems a bit difficult to me...

A more reasonable goal is to become "mortal, but ageless".

But we don't really have any good words for that state.

immortal stems from "im + mortal" = "not mortal".

senescence = "the state of being old: the process of becoming old "

"im + senescence" = "imsenescence"

Still seems pretty clumsy and obscure.

Some other thoughts:

"age-retarded" -- has obvious problems.

"death-resistant" -- not quite, also defined in terms of a negative

"life-fortified" -- sounds like an ad for breakfast cereal

"lifeful" -- hmmm, not quite

"continually rejuvenated" -- accurate, but cumbersome

"indefinite lifespan" -- clumsy

Related concepts:

amaranthine, unfading, deathless, undying
everlasting, eternal, lasting, eonian, aeonian
deific, ceaseless, never-ending, perpetual, unending, eterne
constant, continual, continuous, incessant, interminable, nonstop, ongoing, persistent, relentless, round-the-clock, timeless, unceasing, unending, unfailing, uninterrupted, unremitting, abiding, continuing, durable, enduring, lasting, long-lasting, long-lived, long-standing, old, perdurable, perennial, permanent.

Perdurable is an interesting word - it means "existing or remaining in the same state for an indefinitely long time". But it's quite obscure--I don't remember seeing it before now.

Suggestions?