Loved the story. Never could figure out why Tempus was so galatically stupid and no one pointed it out. By destroying the past he very well could have and should have caused his own destruction. I always thought that by changing what Superman did that someone who didn't die originally would die and that would cause Tempus to be no more. It doesn't even have to be directly related to Superman. But you could have Superman save someone or stop something that in turn causes a person's behaviour to change so that someone doesn't die who in turn saves someone etc etc so that by the time you reached Tempus it wouldn't even be a noticeable act that by destroying Superman brought about his not even being born.
I always believed that not only was Tempus trying to destroy Utopia but was too stupid to realized that he was actually probably destroying himself.
