In the last decade I went through thousands of articles, including smart and junk ones and also red 100s of books on training, biographies, sports science, periodisation. Brad Hudson, Joe Friel, Jack Daniels, Tudor Bompa, Renato Canova, Alberto Salazar.

You can find one very common facet of their approach. They don't take on 50 runners, but just a couple. Why ? Because prescribing effort on paper is one thing. Watching every stride, recording every second on the track, asking personal and sports related questions and looking for changes in voice tone is another.

While you can buy their books and find a lot of great great training advice, you should be actually personalise those to your individual needs ! This is very important. There can be three runners doing 100mile weeks, but one might be running a lot of easy milage, the other would be focusing on threshold and tempo work, while the third one would have short distance, high volume interval sets 5 times a week, while all three of them would be focusing on the same race, preparing to run the same time !

Do not get locked in on milage, on speed of training, on frequency. Feel yourself day in, day out ! I tell you a secret, the effects and benefits of training are more dependent on what you do in-between sessions, than the actual training itself. The runner who can double up days, go to massage therapist, sauna, swimming, lifting sessions and sleep 12h+ nights with afternoon naps, while working with a nutritionist, will get more out of his body on a daily basis. The CEO seated all day, pulling long shifts and sleeping only 6hours a night, having 3 children and worrying about mortgage debts will have to manage running, entirely differently. With a proper approach though, he can be very good too.

I recently started coaching a 5k runner who is a very talented speedy guy. However, he is a maniac in case of work and cycles through the busy streets day and night as a bike messenger at least 5 times a week. We talk about 10h plus riding with a heavy back pack. 100km plus days with D+1000m elevation.

As endurance goes, we don't do anything. No point of long runs, jogging and aerobic development. It is done on the bike.
As speed goes, however, we must really focus on leg-speed and turnover, so 3 times a week we do hill sprints and 50 to 60m accelerations as part of warming up and cool down. Hurdle drills, skipping roping and ladder work.
Our training is mostly 100s / 200s / 400s and every second to third week we add 600 / 800 / 1000. This is coming from personal observation, that despite the very low volume, but fast running, his endurance doesn't diminish ! In 2000 / 4000 time trials , he doesn't loose speed.

On the other hand, I have runners preparing for the same race, coming up in two months. They are going to run fast, but nowhere near winning. We don't do anything under 1000 repeats, because finishing kick is not important, but more likely holding pace, posture and stride for that long.

In regard of this knowledge, I can tell you to not to pick a training program from a shiny magazine's back page. Use the VDOT chart from Daniels' running formula, but be smart about it. Adjust your volume and frequency. Your goal is to maintain long term development and to run fast always. Not just tomorrow or in three months time, but always !
Of course, there is also the minimal effective volume. Running your first ever marathon with 10k a week, will not reap results ! Be smart and ask questions, on the net, from your coach, from yourself and get the answers through a filter !