Right, agreed that the time is the important part. If you can sustain a run for an hour or so a day, that is a lot different than a 20 minute one. And, my assertion is that a lot of the benefit of the extra 40 minutes is the substitution effect.

This is a lot of what I think many studies find that show benefits to coffee and such. Nowadays, that is as often a substitute for sodas. And the amount of calories you get from a soda is just flat out absurd. I'm fairly certain even those of us that know it is bad for you underestimate just how bad it is.