I am not particularly exceptional among the set of human beings, and so should not value my lifespan much more than that of other humans. I obviously fail at this in practice, but I think the world would be a much better place if I and others didn't fail so often.

Are you claiming that this is a true statement about the world or that this is a description of your preferences? In the former case, I'd like to see an argument with that as the conclusion. In the latter case, I would take the fact that you don't seem to act as if this your "true" utility function as significant evidence that it is not your "true" utility function.