Jeff, back in my days of being a "track star" (lettered in varsity track in 7th grade
), I learned that cool down exercises REALLY help with lactic acid build-up.
I don't know much about distance biking, but I do know that the best way to prevent your muscles from performing anaerobic respiration is by being able to feed them through your own lungs. It seems to me like that is not possible with the amount of miles you'll be turning out. Would it behoove you to do another easy 5 or 10 miles with some good breathing the first day to work the acid out of your legs for the second day?