John Walker only hit 100 miles per week but wasn't comfortable and self modulated to 85 miles per week, but that is solid average. the mainstay was like 12 miles in 70 minutes ish per day at 440 to 530mile pace often with hllls. then a long run on the weekend. with a training partner like Dixon or Scott, there would be wild quality in there, so those guys had a lot of fun.
So what is the point?
The athlete had to work with 85 mpw, and that was good enough for OG gold, world record, and 100 sub 4 minute miles, and those were mostly way under 4, not to mention a similar amount of 1500s.
Snell was fixated on the 100mpw. like a mental battle, love hate, for confidence he needed the number, of course the base work laid the foundation, and to mention it was followed by intermediate hill work, springing, fartlik, quality before the track work. Snell would throw in speed work instead of some distance and not tell Lydiard. The intermediate period was around 85 miles a week ish, and the track work dropped down to 50 miles,. racing was even less.
On another front, if you are running well and healthy and full time, 100 mpw isn't that much. If you're not going so well, and working 40 or more hours it can be drudgery. I experienced both, as if entirely different people.
On holiday on 90 mile beach, I'd run beside the surf solo for 2 hours every day, it was so fresh and beautiful, i was excited by lunch time that the run was only a few hours away.
In the winter, there was a bad patch, where it seemed difficult to lift the legs in 15 milers, it was pure uninspired drudgery.
If you hit 100mpw at some point that is money in the bank.
At the end of the day, if you're not feeling it, you have to back off. just run 50 to 70 minutes per day, or two time 30 minutes or some such. when you start to feel it, you can attack the hills here and there,