Hm! I think that they would say that it's a method of attainment, or a key, to immortality rather than the immortality, itself—a human's angelic part is always at least potentially immortal, but it needs to realize its essential contentment through the body's practice of material contentment. (Neoplatonists disagree on the best way to get there—some favored contemplation, some favored magical practices, and to these I would add devotion as a viable path.)