non incorporeal non undead template applicable to humanoids that grants immortality?

[MaxiDuRaritry]

im not interested in life support. im not interested in dying in an amf, dead magic field, after a thief steals the item, etc. i want to be immortal like a succubus is. no strings attached and nothing takes it away. thats why i chose templates. no life support. no horcrux. no achilles heel. just plain immortality, no strings attached.

The only three ways for someone to take your immortality away in the case of a device psychoactive skin of proteus are 1.) to prevent you from ever using your psychoactive skin for long enough that you die of old age (which isn't exactly easy, even if you're metamorphosis'd into a mayfly), 2.) to convince you to change back to your original form after your lifespan would normally be up (which is also not exactly easy, especially if you add a protection from evil effect to it for cheap), or 3.) flay your skin off (in which case, it's easier to just kill you; and you'll probably die from it anyway).

And it's not like you can't do multiples of these.