There are two capstone abilities that grant "cures for aging"
The wizard has the immortality arcane discovery:
Benefit: You discover a cure for aging, and from this point forward
you take no penalty to your physical ability scores from advanced age.
If you are already taking such penalties, they are removed at this
time. This is an extraordinary ability.
The Alchemist has Eternal Youth grand discovery:
Benefit: The alchemist has discovered a cure for aging, and from this
point forward he takes no penalty to his physical ability scores from
advanced age. If the alchemist is already taking such penalties, they
are removed at this time.
But these do not specifically state that the character will stop aging.
The age resistance spell specifically states that it does not stop dying from old age.
You ignore the physical detriments of being middle-aged. This spell
does not cause you to look younger, nor does it prevent you from dying
of old age,
Whereas the longevity mythic ability specifically states it does.
Longevity (Su): Upon taking this ability, you can no longer die from
old age. If you have penalties to your physical ability scores due to
aging, you no longer take those penalties. You still continue to age,
and you gain all the benefits to your mental ability scores.
So does immortality/eternal youth stop aging, or just the stat penalties of aging?
Best Answer
Could go either way, depending on how you read “cure for aging.”
It might just be description—a “cure for aging” which here is defined as eliminating penalties by the rest of the description, which are taken to be the actual effect.
It might mean a cure for the things the game calls aging—the penalties. This is only subtly different from the first, which ignores the phrase as fluff description—this regards it as rules text, but text that is then expanded and defined, not an additional part of the ability
It might mean that you do not age, or otherwise include death from old age as part of aging that it cures.
The first two would still have die of old age, the last would not.
The fact that they are called immortality suggests that the third one is accurate, but honestly it really should say. The wording also implies that you still get aging bonuses, which implies some aging. Effects like these usually spell out what they do, as age resistance does, and these effects ought to as well.