In my training plans and weekly schedule, I always make sure to include what I like to call "absorption" runs.
I believe the term was coined by Steve Moneghetti, and it refers to 30-45-minute runs at a very low intensity pace, so that the body has an opportunity to absorb the benefits of the hard workouts done previously.
Now, I know these runs have traditionally been called "recovery" runs, but I like to think that Steve's rewording highlights their value in a training program, rather than dismissing them as filler between workouts.
So here's to the "absorption" runs, and let's give those "recovery" runs a run for their money! Of course, the big catch here is that you still need to put in the hard workouts to have something to absorb.