HRE wrote:
Three to four sessions a week is a lot of hard running. You might do better with two or maybe three some of the time. But that wasn't your question. Personally, I think that you can overdo the "run really easy on easy days" thing. Peter Snell told me that the measure of whether you're running too hard or not is whether you can do that pace pretty much daily or not. If you need very short and slow days or days off regularly you're running too hard, he said. Eight minute pace was once considered pretty slow. If you were managing it well, i.e., as Peter described to me, I don't see why you'd need to go slower. I'd suggest not doing your distance work as slowly as you've done recently but not doing more than two "workouts" a week.
Wise words! That`s the way to do it! Listen to that advice.