Could the repeating of days in Hopper's life been due to the fact that he was a good detective? Each time he was using deductive reasoning in order to ascertain the consequences of his actions. The trigger in his mind at first was the injection to the neck that caused him to go to sleep and awaken in the same day thus causing him to re-think his theories on the case.I believe a few of the characters were actually his conscience prodding him to take certain actions in order to discover the consequences. A detective uses these types of scenarios to find the best way to conduct an investigation. I think the writers had a good concept and it played out well. Unlike another show to remain unnamed (hint: an island), they had a clear objective in mind and guided us through the series in such a way as to not only keep us on the edge but, also to bring the show to a finale in a believable way.