Today I was stuck on the treadmill because of the plowed snow around my neighborhood, so I decided to mix it up a little bit. I started the first mile at 7 minute pace and dropped the pace by 15 seconds a mile so that by the ninth mile I was maxing the machine out at 5 minute pace,(had a slight pause early in the 10th mile to restart the machine after the hour mark, maybe 25 seconds) then dropped it back to 6 minute pace and went back down to 5 minute pace to run 14 miles. It felt really good, and didn't seem to ware on me as much a hard tempo. I want to try it with my garmin on the road for some loner runs. I know that Mcmillan and Rosa both talk about fast finish runs for long runs, is this something that I could safely do weekly for a 18 to 20? HOw effective would is this type of run? Does it have the same kind of benefit as a harder pace 10 to 12 mile tempo? Just looking for some insight from some runners who have run the marathon, I am moving up from 5k, 8k, and 10k's.