The Feast of Tabernacles is the appointed time when men receive those immortal bodies. These are not given when a person dies. When one's spirit returns to God, it does not have an immortal body. It is spirit, not body. It needs clothing. And furthermore, the spirit has no need for immortality, for it is never said to die in the Bible. We are in need of an immortal BODY. The "Promised Land" is not heaven per se, but a glorified body as Jesus had after His resurrection.