Ok the title is misleading, and I want to look at one specific case.....
...I'm reading Brendan Foster's autobiography...
He seemed to put in several months of steady mileage (say 100 miles per week average, getting up to 130) at 6:00 to 6:30 pace, and he came out off this training and did things like win the English national cross country, and ran the fastest leg in the national road relays...
I realise he probably did some faster runs with his clubmates, but it absolutely amazes me that there are no structured workouts in there....it's mileage, mileage, mileage....for months...followed by astounding performances. (and it's not like he was the most naturally speedy athlete out there...)
Are we overcomplicating things, and massively overestimating the importance of interval sessions for cross country performance? How does everyone think they would get on if they ran consistent moderately-paced high mileage all winter?