Shifting base

Its high time I give a kind of shape or form to the kind of running I am doing these days and the ones I am going to do a few months hence. Most of my runs these days are progression runs in which I start very slow(8-9 kmph) and pick up pace as the run progresses and finish really fast(14-15kmph). These kind of runs are pretty good in the sense that, you dont need an additional warmup before the run as the initial slow pace serves to loosen up the muscles from its residual stiffness coming from the previous runs and also the body gets warmed up(literally), and hence is able to function more efficiently!
Now if I were to be looking at improving my ability at long-distance running, the likes of marathon and beyond, I might need a slight adjustment to the pace of my run and the duration. While most of my runs now hover around the 7-8 km mark done at an average pace of 12kmph or more, I would need to increase the duration of these runs and reduce the pace. So that would mean I would need to run more long runs(10 - 12km) at a slower pace(9 - 12kmph), so that I don't get exhausted at the end of it.
I have been actually stagnant the last three months in that I haven't shifted to these longer slower runs and also that I haven't been running as regularly as I normally do(4-5 days a week).
But I need to be cautious and on my guard constantly when I make a transition from these shorter runs to the medium to - longer runs, lest my body is not up for it as soon as I think it is. Therefore I have deliberately introduced a day's rest in between each of these medium-long runs, which I think should be enough for the body to get rested and be ready for the next run. Given that I start this kind of training
very soon(hopefully), I should be ready to participate in my first marathon(wherever it is) in 4 -5 months time and finish it in a decent time, 3hrs 15mins to 3hrs 30mins, which would be an ideal goal time, given my current fitness level.

I see running as a long-term investment, the fruits of which beccome better as the years roll by. People usually start by shifting from fast-walking to slow jogging, then jogging, then running faster and then taking part in multiple events throughout the year competitively.. I really believe that whatever be the current speed of a runner, given sufficient time(5 - 10 years), he should be able to compete professionally and at the international level, which raises another question: why don't we have marathoners competing at that level, why can't we have runners running times of 2:20:00 or below? The world record is 2:04:55, which no doubt would take a lot of years, nay decades before an Indian can come close to hitting it. But 2:20? I mean, I only know of one runner who can run below that time: K C Ramu(2:19 odd). We should atleast be able to hit international qualifying times for the marathon(America has 2:19 as the qualifying time for its B team for the olympics), what a shame, we can't even come close to that. It is not that Kenyans or another African people have it in their genes and we don't, hell Kenyans practice and train more than most athletes of other countries do. We have had a person named Shivnath Sngh, who ran a 2:12 in the punjab marathon in 1978, so why can't the second most populated country in the world not produce world class marathoners like Singh is beyond me.
Hopefully, with more marathons being held in India, and the number of people participating in this endurance sport increasing leaps and bounds, we should have a lot of people who start training seriously and keep improving their times and after a certain stage, some of these serious runners should take the initiative to go a step further by hiring coaches with experience and then slowly make an entry into the international scene. Whether this would happen, is one thing which we have to wait and watch.