I'm afraid Seth is just like many runners (maybe you or someone you know) that seems to love training/distance more than racing and lowering times. He's got plenty of endurance, as do many serious runners who train hard - but not enough speed to breakthrough. Yet the "answer" Seth and others always seem to come up with is more mileage piled on more mileage. He races, then wonders why he didn't hit his goal.
Reduce the mileage by 20%, and move that energy/time into faster workouts. I know runners in this boat - stuck on big mileage but can't see they are doing the opposite of what they need to do to get faster.