What paths to immortality can my psychic take?

[MonkeySage]

I'm building an abomination psychic in pathfinder, and it occurs to me that psychics have no answer to wizard discoveries or anything like that.

I know about the Mantle of Immortality, which only provides benefits while worn. If he takes it off for any reason, or it's forcibly removed, he'll rapidly age. Given his race, I'm not actually sure he lives as long as humans do.

Cyclic reincarnation would require him to die in the first place, which kinda defeats the purpose, and relies on an external person to reincarnate him.

It would not be in character for him to seek to become a lich (even if he is possibly slightly evil- he's chaotic neutral with leanings towards evil).

Vampirism is completely off the table, since he wouldn't even be himself if he became a vampire.

I also looked into Formless Adept- it doesn't actually look like it'd work.

EDIT: I looked into the description of Astral Projection, and the only thing that he'd need to worry about is his silver cord.

Would creating a timeless demiplane and astral projecting work?

Mainly, I'm looking for such options because I don't actually know how long this character would live. I don't know if his race lives as long as humans. Would really suck if he died of old age in the middle of a campaign.

[SimonMoon6]

A 9th level psychic spell is "Major Mind Swap". This is Pathfinder's official version of "True Mind Switch". Because True Mind Switch might be too powerful, Major Mind Swap has the limitation that you can only target a creature of your own race. Nonetheless, it is an instantaneous effect that can give you a new body once your current body gets too old and yucky, even if that body has to be the same race that you currently are.

This is in the same vein as cyclic reincarnation (in that you don't get to keep your original body) except that you aren't relying on someone else to cast the spell and you do it before you die, so it has those advantages.

[Psyren]

If you'd rather keep your own body there is also Sun Orchid Elixir. It's very hard to get in-universe (it's sold at auction) but if you locate the buyer or a near-epic alchemist that you can dominate/kidnap/etc, that's another way.

[Arutema]

If you can make it to level 20, you can take the Artificial Ascension Psi-tech discovery (Occult Realms) and upload your mind into a robot. Though access to a suitable robot is unlikely outside a Numeria campaign.

[TheTeaMustFlow]

Would creating a timeless demiplane and astral projecting work?

Can't see why not, if you're willing to deal with the not-insignificant drawbacks of the spell, and the steep requirements for setting the combo up in the first place.

The Celestial Obedience of Lymnieris's third boon (accessible at 20th level or HD, or 9 levels in the Mystery Cultist prestige class to get it earlier) allows you to revert a creature to the previous age category once per day as a touch attack - meaning not only do you get immortality, but you can bestow it on others as well, with no price tag or ethics questions attached.

Apart from only being accessible at a very high level, the biggest issue with this is Lymnieris's fluff, which could be politely described as specific and may well not be appropriate for the character or the game. However, I don't think it would be unreasonable to ask a DM to reflavour the Obedience for another deity or outsider with thematic links to change, rejuvenation, or similar.