I've been doing it since the first of the year, until this week because of the amount of snow, but normally my week looks like this:
Mon: 13-15 easy
Tue: 10 @ about current marathon pace
Wed: 15 easy
Thu: 12 fartlek w/ strides/hill bounds/whatever
Fri: 18 easy
Sat: 1warm + 10hard, faster than marathon pace
Sun: 3 hours easy, usually about 22miles, give or take depending on how I'm feeling
It'll change once base training is over...I used to do another slower run at another part of the day but stopped doing it because it takes up so much time to do 100 in singles and then about 30 or so more at the other end of the day. The important thing is to do whatever it takes to recovery by the next day, and that means proper nutrition.