I think that most people are able to at least implicitly bite the bullet of continuous personal change. And that is why they apply some reasonable temporal discounting. Here is an SMBC that explains the basic concept. One of the very weird things about LWers is their aversion to discounting. Eliezer even wrote an emotional post about it once. Normal people can discount the preferences of their futures selves, current others and future others in a way that saves them a lot of ethical/philosophical headaches.