Pondering what it would actually beworth being in a 'real' paizo world...
In order of ease and power.
True Immortals: Druid (Reincarnated Archetype) 5, Alchemist 16 (elixir of life: you can fake it with cost and warning), Oracle (Heavens/or any with the Enlightened Philosopher Archetype) 20, Monk (Monk of the four winds Archetype) 20,
False Immortals aka the ageless = plastic surgery and roids: Druid 15, Monk 17, Alchemist 20, Wizard 20, Oracle (Time) 20
Sad that alot of the capstone immortality powers do nothing for death or maximum age.
Enlightened Philosopher it is..