In the world of anime, there apparently isn't a consensus on how long an anime should last. There are some anime like Hellsing which only lasts 13 episodes, while Case Closed/ Detective Conan has like 570 episodes. Now, I know that some anime are based on manga that run dozens of volumes, while others are made up by a writing staff, but assuming that they are made by a writing staff that doesn't make filler, how long should the optimal run be?