Longer runs are great, but you do hit a point of diminishing returns. I tell anyone looking to get into running long distance that after a half marathon you are

Longer runs are great, but you do hit a point of diminishing returns. I tell anyone looking to get into running long distance that after a half marathon you are no longer really doing it for fitness, it is about the personal challenge, which is great, but it is important not to trick yourself into thinking more will always be better for you with running. There are also pros and cons of shorter and longer distances. Ideally you are running faster on shorter runs and a bit slower on longer runs. Getting in HITs occasionally will improve your long speed and help prevent injury. It is also a great thing to do on days you only have 10 minutes.