Let's take a look at masters champions like Ed Whitlock who ran a sub-3 marathon after the age of 70 on "plodding for 2-3 hours" or the new over-70 mile record holder who ran only once every three days. Their training is completely opposite each other and neither mean anything for most runners.
1) They are super-responders. With any given training stimulus, most people will have a modest and temporary improvement. A few people will have no discernible benefit and a couple will actually get worse. There is also a small number who get far more benefit than anyone would expect - the super-responders. They are the people who will tell you that you're training wrong, that you only have to do a small amount of one specific type of training, that they've discovered the "secret" to running faster. This has been evident since the time of Roger Bannister running a 4 minute mile done by a few (very fast) miles three days per week.
2) They are bio-mechanically sound. If you watch a marathon, you'll see that the first runners have almost identical strides, especially if you focus on their legs (Bill Rodgers was famed for swinging one arm wide to counteract one short leg). The longer you watch at one point of the race, the more variety you'll see in strides, because they have some structural inefficiencies for which they have to compensate.
3) They never get injured. Because of #1 and #2 above, barring accidents, they never get seriously hurt. Doing a lot of training, whether in the short term, or over decades, on an unbalanced body, will lead to overuse injuries. They also rarely take risks - if you could win a race easily, in say 17 minutes, and you could do it in 15 minutes in an all-out effort, you'd probably run just under 17 (if the record is 16, then you might run 15:50), conserving your effort for more races and more easy wins.
The more risks you take and the bigger the risks, the more you get injured. The harder you train, the more you train, the longer you train, the more you get injured.
4) They don't show the signs of wear and age. This, to me, is the most unfair cut of all. Besides being genetically gifted with the ability to get huge benefits on minimal training and being gifted (randomly, it appears) with no structural anomalies, they are also gifted with less age-related decline. Guys who are winning my age class look 10-15 years younger than I do; part of this is socio-economic, part lifestyle, but also partly genetic. They have won the genetic lottery three times, yet are competing on an equal footing.
5) They quit when it gets hard. Herb Elliott retired from racing at age 22, undefeated at the mile, creating a "no lands left to conquer" legacy. I think he quit when it looked like his supremacy was in jeopardy and, having never taken a risk, never found out what his real limit was.
People who knew Steve Prefontaine say he worked harder than anyone else because he did workouts no one else could do. He had a VO2max of 84.4 and a maximal heart rate of 214; he simply was physiologically capable of workouts others couldn't do, but I don't think he worked any harder. To see what I mean, look again at the finish of a marathon; the winner invariably looks fresh 5 minutes after the race, but those trying to break 3 hours and falling a couple of minutes short sometimes are staggering and collapsing. I say the guy who's staggering, who will be going down steps backward the next day because his legs don't work, worked harder than the winner.
Top runners quit when they have their first serious injury. They won't work harder for less success or risk making their injuries worse. Instead, they write books on how to train like they did. You are not like them. Chances are, you are not like me either, with 5 career-ending injuries (both Achilles, left knee, left hip, right lower back), with 40 years, 650 races and 100000 miles on your legs, 30 years past your last PR and competing against guys who don't have to fight hard just to finish in the middle of the pack. The difference is: you can't be like the champions unless you're born to it, but you could learn from my successes and many, many, many failures.
I'm going to write a series of posts on training for older runners. It will not be like what's already out there. I hope someone finds it useful.
And happy new year!