Everyone needs a mix of activities which waste their time, but might be fun at the moment, and activities which do not. Some of these activities should be about preparing for the working world, some of them should be about staying healthy, some of them should be social. Running can fit into any one of these categories and most likely will change categories as time goes on.
On your death bed, I doubt you are going to say I should have watched more TV. Unless you have a reason to believe that on your death bed you might say I wish I didn't run so much. I would keep running.