Take one year to work up to 100 km of running per week, increasing
your average weekly running distance no more than 5 km / week per
The run 100 km a week for at least a year. I recommend a six day
weekly schedule 15,18,15,18,15,20-25,rest. Then three months before
the marathon, every other week start increasing that long run 5 km
per time, e.g. 20,25,30,35, to 40 km.
In Americanese 100 km = 62 miles, 15 km = 9 miles, 40 km = 25 miles,
5 km = 3 miles.
(In my opinion, 3-6 month training programs from less than 50 km
a week are like binge diets- temporary and painful.)