When I lived in Hawaii, I actively participated in an amazing running club. Well, “club” might be too formal a term. It was an open-to-all, dues-free, super friendly group of people who ran and socialized together. This group met for a run/potluck combo every Tuesday. Those Tuesday evenings were good times. We often celebrated birthdays and anniversaries together. Some of the night owls would stay well into the night.
Anyhow, besides Tuesday, many of us also ran together on Thursdays for a short run as well as on Sundays for a long run. For Sunday’s run, we always ran the out and back Honolulu Marathon course. Depending on how many miles we wanted to do, different pace groups would simply turn around at varying points along the course.
One time, before we started our run, people were discussing how many miles they wanted to run that morning. One guy said, “I think I’m going to do 20.” Another guy replied ‘Ok, cool. I’m thinking I’ll do 22.” And then another guy said, “I’m going to do 24.”
At the time, even though I had to laugh at this display of one-upmanship, I’m pretty sure I thought the longer your longest training run, the better trained you would be for your marathon. It’s intuitive, right?
Well, just as in Part I of this post, the issue at hand comes down to a matter of recovery. The longer the training run, the longer the amount of time needed to recover from that effort. Since people recover at different rates, a 24 mile long run may not be so damaging for one person. However, for MOST of us, especially those of us who may not be natural runners, a run of this length is much too damaging to benefit our training and racing goals.
Perhaps you have heard of the Hansons Marathon Method. This training method is famous (or maybe infamous) for its philosophy on the long run distance. The cookie-cutter training methods in the back of the Hanson’s Method book have the long runs distances peak at 16 miles. Now, to say that the Hanson’s method prescribes a maximum long run distance of 16 miles for every runner is something of an over-simplification. Rather, the Hanson’s method says this:
‘Advice from renowned running researcher and coach Dr. Jack Daniels provides a basis for our long run philosophy. He instructs runners never to exceed 25-30 percent of their weekly mileage in the long run, whether they are training for a 5k or a marathon. He adds that a 2:30-to 3:00-hour time limit should be enforced, suggesting that exceeding those guidelines offers no physiological benefit and may lead to overtraining, injuries and burnout.’ 
I have to tell you, that although I don’t believe every aspect of the Hanson’s method is right for every runner, I agree with their long run philosophy WHOLEHEARTEDLY. From an anecdotal standpoint, it worked for me:
After I had my son, I wanted to get back to marathoning as soon as possible. However, my son was exclusively breastfed, which necessitated him eating at least every three hours. Well, that’s kind of a joke. He was colicky and hated to sleep, so in reality he was eating what seemed like every 15 minutes. I pumped milk every day just to have enough stored so that I could go for a long run on the weekend. Still, I knew that I could not possibly be away from my son for the time it would take to run a 20 miler. So I tried out the Hanson’s philosophy which significantly reduced the time and distance of my long runs.
Believe it or not, just 7 months after having a c-section, I PR’d at my next marathon by over 3 minutes on an extremely difficult course.
Now, I cannot say that race result came solely from a change in my long run distance. I made a number of other changes as well which I will talk about later (also, there is much anecdotal evidence to suggest that pregnancy can have a positive effect on performance). Nevertheless, for my next 4 marathons following this one, I never ran a training run longer than 17.5 miles (usually less), and I PRed EVERY SINGLE TIME, including when I finally Boston Qualified.
 Luke Humphrey, Keith Hanson, and Kevin Hanson, Hansons marathon method : a renegade path to your fastest marathon, Kindle Edition (Boulder, Colorado: Velo Press, 2012, location 854)