Where we're at
Kurt has run a 16 mile long and turned in a quick 50:12 10K; I've reached my first 20 miler but haven't run a time trial in weeks due to the heat and travel to North Carolina (the last time trial was in early June, a 7:44 pace 5K, my fastest 10K a 50:28 in late April). Today we both ran half-mile intervals, averaging seconds just below and above 7:00 paces (3:30 halves). I don't think we're that far off; Kurt has successfully overcome the stress fractures, adjusted to the orthotics, and gotten on track with a program that has little room for downtime; I've avoided overuse injuries so far, in particular the IT band, with extra rest and an elongated program.
Driving down 10K times
Seven weeks to go before tapering. Despite what some of the calculators say, I'm not confident we can take current stamina levels, add several 20s, and make the sub-4:00. Assuming I could run a 50:00 minute 10K, I think we need a bigger cushion -- maybe drive the 10K times down between 47:00 to 48:00. Why? At the current 50:00 10K times, Coach Bensen's effort-based training charts say we'd be running our 8:45 targeted marathon pace at 80% effort, which the coach says is not likely sustainable over 26.2 miles for rec runners. A more realistic and sustainable effort might be around 75%. If you can run a 48:00 10K, a 75% effort translates to a 8:49 pace. For 47:00 10k, it's a 8:37 pace. So you can see the effort becomes less -- and easier to sustain -- as you drop your 10K times. This assumes you've put the endurance part of the equation in place; in other words, run your 3-4 18-20 milers.
The biggest risk
The main thing is to continue to do the once a week intervals/tempo runs, the marathon pace run, and the long -- WITHOUT overtraining. If I feel tired or have a strange tightness, I will drop any thought of a fourth run for extra rest, and sacrifice building mileage that week. The biggest risk in trying to drive down the 10K times is getting hurt by doing too much and being too aggressive. But I think we're on the right path.