training is about mixing it up, we did 7 total today some tempo and added a nice hill at the end, I am starting to get a new theory about wearing myself out, or at least to a point near exhaustion but not too sore, as a goal,  Sometimes that comes with a little effort and sometimes with a lot of effort, time is not neccessarily the goal either, just bringing your body in a workout and over a few days of workouts to the point of needing to recover, or forcing your body to get stronger to deal with the demands you place on it, for this to work and not crash your system you must be in tune with you.  I believe that most people are afraid to push their body to this limit, some people push over this limit and this is also not good, but finding the limit is the true goal.  You can go hard or you can go home, but not both?