dnixon, i'll throw my 2 cent in also regarding schedule of a typical 100 mile week.
before my best marathon i did 5 weeks of 100+, 2 weeksof 96, and 1 week of 92. i also cut back 2 months before the marathon and did a month of 75mile weeks with more intensity.
first off, i am not married to 100 miles, just close to it, if it ends up being 96 miles, so be it, i don't try and make up the miles in any way. conversely if it ends up being 102 or 104 that's fine also. i keep it pretty simple and then improvise a little as the weeks unfolds.
Mon: AM-8 easy. PM-8 easy with 10 x 20 sec. strides in the middle of the run
Tues: AM-8 easy PM-8-10 including some sort of track workout, anwyhere from 12 x 400 to 3 x 2 miles depending on where i am in my schedule
Weds: AM-8 easy PM-8 easy maybe with a few pickup miles at the end depending on how i am feeling. closer to the marathon i will do a 12-16 miler on Weds, usually shortening the morning run or dropping it altogether
Thurs: AM-8 easy PM-8-10 with some sort of tempo run of 2-4 miles generally
Fri: day off-for some reason i like taking a complete day off without thinking about running
Sat: Long run of 20-24 miles easy early on in the training. adding harder components as the program progresses, such as last 6-10 miles at goal MP. i will also take cutback weeks on mileage where i only do a 14-16 mile long run with possibly 4-6 hard in the middle or end of the run, close to 1/2 marathon pace. the hardest long run i have done is a modified Khalid Khannouchi run where i do 3 miles gradual warmup, 7 miles at goal MP plus 15 seconds a mile, 10 miles at goal MP, then 2 miles on the track to finish at LT (tempo) pace, about 30 seconds faster per mile than goal MP. boy, did that one kick my butt. usually do it 4 weeks before the marathon to get a good recovery after it.
Sun: 12 very easy
i usually do incorporate cutback weeks, usually around some goal races with in the program. cut back to about 60% mileage for those weeks. for some not so important races i train through them. nothing like a 10K race on Sunday after a 100 mile week abd a 20 miler on Saturday!