Life has got a habit of not standing hitched. You got to ride it like you find it. You got to change with it. If a day goes by that don't change some of your old notions for new ones that is just about like trying to milk a dead cow.
Now I say that if you run more than 15 miles a week it's for something other than aerobic fitness. Once you pass 15 miles you do not see much further improvement.