I keep reading a common training rule that the long run should be no more than 20% of the weekly mileage, usually referencing Daniels (I think) ideology.
Is there a specific reason for this? High risk of injury, some other physiological reason?
Definitely feel like I get more out of a longer long run at good clip and having the rest of the week be solid quality, than having a shorter long run and having to do more junk mileage (long cool downs/warm ups).