It's an ongoing debate.
Quantity of miles or quality of miles?
A local running coach, I'll call him Coach A, makes shirts saying "Do Miles". That could be just a shirt declaring someone is a runner but it's actually the coach's philosophy. Go out and run more and more miles. Miles is what's important.
Another local coach, Coach B, is about quality of miles. Each mile should have a purpose with no junk miles.
In the world of supersize, we think more is better. If 30 miles is good, 50 miles MUST be better. Even I look in awe at people hitting 50 miles or 70 miles in a week. I hit 50 miles once and felt I had accomplished something big; I proudly posted I hit 50 miles that week. The fact within 2 weeks I was injured isn't irrelevant.
But wait...elites are running 120 miles a week so isn't that support to run more miles? The important thing to know is the elites are running those miles as quality miles. They are doing speed work, putting in goal miles, tempo runs and long runs. Each run has a specific goal. You won't hear the elites say they are slogging through the miles.
Training Science blog posted An Interesting Analysis of Some Elites' Training History and are proponents for the theory that high mileage doesn't lead to increase performance with examples of Ron Hill, Alberto Salazar and Bruce Fordyce. Each elite runner they tried the more is better approach and had increased fatigue and decreased race performance. The elite runners experiment of more miles equals more success failed.
In the book Lore of Running by Tim Noakes in Chapter 5, Developing a Training Foundation there are 15 laws of training with law #6 with Achieve as Much as Possible on a Minimum of Training. Noakes says "But since the first running boom of the 1970s, an increasing number of runners have begun to believe that the more they train, the more successful they will be. In fact, there is a limit to the amount of training the body can benefit from. Training beyond that limit produces progressively poorer performances, leading ultimately to overtraining". The chapter discusses the importance of quality over quantity.
What about you? Which camp are you in?
Quality or Quantity or a mixture of the two?