What I meant by ‘every second counts’ was for someone running far less mileage than an elite runner the gain from speed work will likely be less than the gain from increased mileage.
The marginal gain from speed work will make a bigger differrence to an elite runner where the difference between winning and losing can be a few seconds. A few seconds off my pb would not make much difference especially compared to the greater gain I am can achieve through higher mileage.
And regarding the small range in my weekly mileage thats because of the way I structure the weekly long run (on Sunday)
6 days a week my mileage doesn’t vary (although the workouts do).
Mon: 8 Easy
Tue: 8 Tempo or Marathon pace or Hills
Wed: 16 Easy or Long run pace
Thu: 8 Tempo or Marathon pace or Hills
Fri: 8 Easy
Sat: 13 Marathon pace
The mileage 6 days remains constant; which workout I do on Tue and Thur depends on how far out from the race I am. So does the number of miles done at marathon pace on Sat.
The Sunday run varies based on the following pattern:
Alternating Sundays I do the same workout as Wed (16). I consider this a rest week. The alternating Sunday I run from 18-24 miles. The closer to the race the longer the run.
And, besides the spring goal race I do 1 or 2 fall marathons. These races are not primary goals but help to break up the training year. They let me race under different conditions than found at the Long Island marathon.
After the fall races I build mileage back during the next 4 weeks (in December). I do the same after the spring race (in May) so for 2 months out of the year mileage is somewhat lower. Giving me a mental and physical break from training.