With the TMRE spoliers, I think I begin to see a greater pattern to the way immortality functions in ArM:
*Great Elixir (TMRE)
You become a fully immortal magical or faerie humanoid creature, but you lose the human faculty to learn and improve. You need magical rituals to accomplish any kind of self-improvement.
*Inner Heartbeast (HoH:MC)
You become a fully immortal magical sentient animal creature, but you lose your human body and the ability to learn and improve. You need magical rituals to accomplish any kind of self-improvement.
*Living Ghost (TMRE)
*Guardian of Nature (HOH:MC)
You become a fully immortal spiritual ghost-like or nature-spirit-like entity. but you lose freedom of movement. Your lifeforce is bound to a fixed location, that you cannot leave.
*Immortality of the Forest (GotF)
You get full immunity from age, but you are fixed to a geographical area (albeit larger in scope than for LG or GoN) and you ultimately face earthily demise in Final Twilight.
*Longevity Potions with very high lab tot (ArM)
*high Divine aging-retarding Method/Power total (RoP:D)
You are almost, but not quite, immune to aging, and you keep all human qualities including learning ability and freedom of movement, but you ultimately face earthily demise in Final Twilight.
*Path of the Body : threshold of corporial repose (HOH:MC)
*Shaoshayant's Elixir (RoP:D)
You get full immunity from age, but you bound to a very strict code of behavior, and you ultimately face earthily demise in Final Twilight.
*Ascension to the Hall of Heroes (TMRE)
Dunno about this. Is the character still playable after it becomes a daimon ? I doubt it.
Plus, I guess there are likely mystical methods to use infernal powers to delay or stop aging, making one partially demonic, or even turn onself into a full demon in RoP:I, even if I'm not fully aware of their scope and characteristics. Lucky owners of the book and authors are welcome to contribute to this list.
There are two important thematic points to this, IMO:
The Limit of Aging is far from absolute. It is relatively easy for a dedicated magus to break it with Mystery Initiation. As a matter of fact, the Limit of Aging is one of the lesser limits that is more easy to break with mystae, with several different methods and options. This may reflect something about the nature of magic, life, the soul in the ArM setting, or just the fact that cheating age and death is one of the likely foremost objectives for the average mage researchers, and this limit simply got more research effort from Hermatic mystagogues than say the Limit of True Feeling, and with a comparable effort, all lesser Limits may be similarly broken or sidestepped.
As it can be seen, with Mystery Initiation any mage that despises aging or the afterlife and is hungry for unlimited time on Earth and immunity from death can rather easily overcome the Limit of Aging and get full immortality under an array of options, but he must still accept that he will meet ultimate demise in Final Twilight or give up a fundamental human quality (freedom of movement, freedom of action, human body, unlimited potential for change) or a combination of both. Cool, nice steup. Much, much satisfying than making the Limit of Aging an impenetrable barrier, IMO.
I especially appreciate the fact that under this system, if a mage is really willing to pay the price, he can even cheat God and the Devil of one's soul. Of course, one might state that a mage turned faerie/spirit/magical creature is not really escaping the Divine's judgement at the end of the world, or that (more likely) the Divine ultimately lets the mage have the kind of eternal existence that the mage really wants, but the (thematically very important IMO) point is that the game system makes the Church provably wrong and that Hell is not the inescapable afterlife fate of all those who reject it. Of course, one might even argue that the soul goes to its preordanied (sp ?) destiny and Hermetic magic, even empowered and broadened by the Mysteries, can only have dominion on the body and mind of the magus. This cannot be disproved, as it cannot be disproved the alternative explanation that the Divine simply leaves the soul free to go or stay where it really wants to be. This is left to the individual troupe to decide, even if I think the second solution is much more rewarding for most players: of course, my opinion may be biased by my intense loathing of Middle Age Christianity/Islam.
A thematically important issue that remains unsolved is what happens when the mage has conflicting allegiances and mystical bindings to one's body/mind/soul: e.g. what would happen if a diabolist would undergo the ritual to become a spirit or faerie ? Would it fail ? work ? tear him apart ? turn him into a demon instead ? Can a non-infernal, non-divine immortality method allow to cheat an infernal pact ?