At his least realistic, which tends to be when he's on drugs in his twenties, Alec thinks immortality is either attainable or already in his grasp. However, even someone as fit as Alec isn't immune to the realities of aging, so as they start to set in during his late middle age Alec simply decides not to think about it. One day he sits down with Viola and tells her to draft a will for him, that he will leave everything to do with his death and the time after to her, and then from then forwards he does his level best to ignore it. He doesn't handle it well.