"I have a question regarding your 10% increase every three weeks. How would this work if I were training for a marathon? Would I have to do a 20 mile run five times a week? I'm sure that can't be good for your legs. Do you have another training schedule that you recommend for marathons? Like your friend in the article I have also had IT band problems, which I believe was due to increasing my mileage too fast when training for my second marathon. Thanks for any help you can offer."
In my humble opinion, it takes right on the verge of four years of consistent, (preferably) injury-free training to go from couch-to-marathon. When it comes to the "marathon puzzle," every athlete is an experiment of one.
Here are the assumptions I used in answering the question and laying out the plan:
First, at least one day of no running each week. The physiology guys have recommended a day off each week per decade over the age of 30. This can a blessing or a curse, especially for the runner who loves to get out and run on impulse. The mother of one of my "summer vacation" athletes told me the other night, "...oh, she got bored and went out for a three-mile run." When the training volume goes up the rest day (and recovery!) becomes more important, not only for physical but also for emotional benefits. Running is hard enough without upsetting your spouse, significant other, employer, friends, and so on...
Second, the long run should be no more than 25% of weekly volume. This is especially important when the volume increases to training for half-marathon or longer. Some of the 'high-mile weekend' plans I've seen have relatively low-mileage weeks leading into them. When the long-mile day in some plans is up to 50% of a week's training volume it puts too much importance on that one single workout. A bad day or bad weather conditions can get deeply into the athlete's head. And when it comes to training, the athlete's head can be a very scary place in which to instill disbelief.
Third, run a variety of workouts. My group trains up to 90 minutes each time twice a week on the track. One day we run distances ranging from 160-to-400 meters, the next day we run distances ranging from 400-to-1000 meters. The efforts range from aerobic to acceleration drills up to VO2max pace. Almost every workout is based on perceived individual effort; no stopwatches unless we're focusing on a shorter race when we try to run a specific time for a repeat. Efforts for training runs range from very easy for the long run, to fairly intense for the track pieces. The runs which aren't long or track-focused can vary in pace from aerobic to lactate threshold pace, times where the body/mind is taught to run efficiently using different energy systems.
Marathon training is difficult enough to complete without the athlete boring themself into injury, so a variety of run distances and intensities can make the cycle less daunting.