Bates Motel is a superb example of a TV series that benefits by knowing the duration, as well as the content, of its end game. This season, pre-announced as the show’s last, allows the writers and producers of Bates Motel to work its way up to the contents of Alfred Hitchcock’s 1960 Psycho film, which inspired this series. But it also allows it to do what the movie didn’t, which is to get inside the mind of Norman Bates. Deeply, deeply inside, where his dead mother, Norma, still lives…