to go fast you first have to go slow....
Not true. No reason why some intensity cannot be introduced early. The amount will depend on how well and how quickly recovery occurs. Beginners will yield gains almost regardless of what they do. But after that adaptation occurs when the systems required are pushed to their limits. Then you recover and the system improves. This is basic concept of supercompensation. By only doing slow miles for a few months is getting you good at slow miles and not much else.
that means base miles. i don't know if you schedule permits you more time for longer riders but if i were you i would try and getting more rides of 2hrs or more regularly....rides of 3hrs+ are optimal because this is the point at which your metabolic rate will change more quickly if you are regularly riding more than 3hrs.
Optimal? Decided by what? Metabolic rate of what?
i realize this is not possible for most people but again if you can fit it in, then it will make a big difference. it is important to go slow initially to build a baseline level of fitness. this will be a a foundation on which you will build for the future. it is similar to a pyramid. the more base miles you put in, the higher the peak...or faster you can go.
The more mitochondria you have, higher VO2max (and power as percentage of vo2max), gas exchange, processing of metabolites blah blah etc etc, this makes you faster. This is not dependent on base miles.
if all you do is short intense rides(like you have outlined) the body will not respond as quickly to a truly long term metabolic change.
The body responds very well to short bursts of intense exercise. You use the term metabolic change... I do not think these words mean what you think they mean.
the intensity will eventually cause the body revolt and have periods of heavy fatigue because it doesn't have base fitness to draw upon.
Nonsense. Fatigue does need to be managed AT ALL TIMES but there is zero physiological reason why intensity ("threshold" and above) cannot be done year round. For my riders who have a proper off-season the majority of work they do is FTP and above.
if you do the exact plan you have outlined but rather than go hard simply go easy and slowly start to increase your speed, then you will get better results. easy your body in to the level of fitness. trying to go all out right away will shock the system and take you longer to reach a higher level of fitness. if possible, long slow rides, then after a period of a few weeks or even a month increase the level of intensity.
As I posted above, I think it lacks intensity, there is no drive for the body to up the things which wil improve speed.
If I get more than 5 minutes free I'll post the corresponding studies which help to highlight why intensity rocks.
LSD can and does have a place in a training program especially if the rider is doing a race of any decent duration but having a "base" and this base being essential is just fantasy and is dictated more by tradition than any real science.