Eternal life is not a gift, but the atonement of endless reincarnations; Dave's long loneliness is to save his beloved in reincarnations again and again, who will eventually forget him, until he saves enough redemption and breaks the shackles of eternal life.
All times, all encounters, and all partings are not accidental. Dave's immortality stems from a selfish obsession a thousand years ago. He is trapped in the reincarnation of the human world. He will always live, always watch the rebirth of his beloved, always be forgotten, and always watch the end of the other person. His long time was never one of suffering alone, but a one-way protection and self-salvation that no one knew about and spanned thousands of years.
Intention: Eternal life is not a gift, but the atonement of endless reincarnation;