Some questions spring to mind with your first post. They revolve around the feeling that you seem to be aiming for ever-higher mileage without trying to maximise your race performances at each stage of your development.
You should be able to carve out a solid 10k time on 70-75 mpw without feeling that you will achieve nothing noteworthy till you reach 100mpw.
I would recommend that you stick with the 70-75mpw level until you are sure (after 6-8 weeks, at least) that you can deal with this mileage comfortably IF IT IS ALL EASY RUNNING.
Even having achieved this, it?s nothing special. You are trying to change the muscle infrastructure in your legs. And that takes time? even years. You cannot say, ?I?ve reached 75mpw? now what??
(Don?t look down on 7.30-8.00m/m. Jason has posted a number of times that the elite Japanese marathoners run this pace for many, many miles in training).
So, if you are sure you have this 75mpw sorted, then I would suggest you take two days per week and run them hard. You are trying to reach a stage where you are convinced you cannot get faster at 10km unless you increase the training mileage. Only THEN, move up.
On the two hard days, I would recommend the following (always after proper warm-up, etc):
On one day, run 2 x 5 miles @ 10km road race pace per mile plus 1.00m/m
(eg: if you can run 37.00 today (5.57m/m), then run 2 x 5 miles @ 6.57m/m with 2-3 mins easy jog break in the middle.)
At first glance, you are going to think, ?that?s easy?, but the point is to do these every week until they become so comfortable that you could continue for ANOTHER 10 miles if requested.
Continue doing them until you think nothing of doing them without the break. (It might be helpful to have a HRM here and note that the HR should NOT climb throughout this run, but be steady after the first 10-15 mins. If it climbs, you are not comfortable enough and need to keep doing them at his pace before doing them faster.)
Once they become comfy (let?s say in 6 weeks), run them at 10km race pace (which gets adjusted as your performance improves) plus 50 secs/mile.
After another 6-8 weeks, run them at 10km pace plus 40 secs. Never run them any faster than this. And if need be you should ALWAYS be confident you could go round again.
On the OTHER hard run per week, run 5 x 2000m @ 10k race pace with 3-4 mins easy jog recovery. This can be hard work as your 10k pace gets faster, so don?t approach this session lightly. Make sure you are fresh and ready to work, and not somewhat run down from the rest of the week?s training. If need be, start with 3 x 2000m for 2 weeks, then 3 x 2000m for 2 weeks, then 4?
The rest of the week should be easy as possible. 10k pace + 1.45 ? 2.00 mins per mile is fine. (or maxHR minus 40, or even 50bpm) Long and easy.
Race a 10k every 3-4-5 weeks or so and watch your times come down.
ONLY when you are running 10 miles @ 10k pace plus 40 secs (and it?s so easy you could go round again), AND 5 x 2000m @ 10k race pace with 3 mins recovery AND you are sure you cannot get any faster over 10km, should you move up in mileage.
The better you do this phase, the more you maximise your performance NOW, the more you will benefit if in 18 months, 2 years, or whenever, when you decide to move up to a marathon. Then the move to 100mpw + will be smoother, and you will be confident that you can take your race pace per mile at 10km (however fast it is by then) and add a maximum of 30 secs per mile and run THAT pace in your first marathon. I?m a big believer in doing a thing properly and am often telling others, ?Do it once. Get it right.?
As always, back way off on the mileage and intensity every 4th week for a breather (maybe as a taper for a race?). You are in this for the long haul, skipping these easy weeks because you think you maximise your time better by doing lotsa miles, is just a false economy which may come back and haunt you later.