If you google Marathon Plus about how many miles they last, you will find forum discussions where actual users are getting between 6,000 to 8,000 miles of loaded touring on them. HOWEVER, I'm not too concerned about those sort of miles, or flat resistance as I am with a greater degree of comfort.

I'm not so sure myself in regards to rolling resistance test, but there is only one place that does these tests, and I don't think they're malarky, but in the real world I don't ride with a problem bike, if I did, I wouldn't spend more money for better tires to put on a bike that is wreck...just sayin, so I don't think in the real world there would be a lot of difference, but even if there is say a 5 watt difference in the real world vs the testing machine, ok, so what? all that means if I got a different tire that used 5 more watts on the test than a different brand, I would still be off by 5 watts in the real world just higher than the different brand; in other words, it would all equal out.