As Nobby has said it is really important to remember that the whole deal with schedules is a guide.
As one of the guys who struggled to get to 100 miles a week I found that for me the long run was the key.
Basically when I started I always wanted to run 20 to 22 miles but then I found I went to the 2 to 21/2 hour club.
I probably went to the time factor because when I ran with Bill Baillie in the early 70's he had bad achilles tendon problems and we would literally shuffle away from his house at 10 - 12 minute mile pace. As we progressed and warmed up so the pace lifted. I don't recall finding the pace difficult at the end on those runs but we were not jogging along looking at the daisies.
Some Sundays I would not know how far I went, others I knew exactly. One year I ran 22 consecutive 20 milers (Cross Country)in Cornwall Park in Auckland for no other reason than I could not get over to New Lynn to run the Waiatarua,
(I was a poor student at the time).
That year : Mid week I would generally run 2 other runs of around 1 to 11/2 hours as well.
At the time (1978)I was not competing or that interested in doing so but assisting others with their work. ie training hack.
Sometimes the whole week could depend on what someone wanted to do. I ran a lot with a guy named Howard Healey who that year placed 5th in the Commonwealth Games 3k Steeple. Behind 3 Kenyans of course !!
Howard had also been Coached by Bill Baillie at one stage,
To me it is consistency of miles (not necessarily 100 per week) consistency of days, consistency of months, consistency of years. You throw a long run per week into that mix and you will go places.