Most of my hiking has been in Oregon and Washington, but here's my take on trailrunners.
I read one of the Army studies, and they did find that a pound on the feet is equivalent to 4-6 pounds on the back. The effect is greatest when moving fast, like running, like a soldier might.

How durable trail runners are depends on how you walk and how heavy you are. My first pair of Altra Lone Peaks (3.5) are still wearable after 1000+ miles, but I only weigh 120lbs., and am pretty easy on shoes in general (and they're pretty patched up, inside and out.) I would think maybe 300 miles would be a reasonabl expectation.

I like the Altras, particularly the wide toebox, and they now have wide sizes as well. The "zero drop" took me months to get used to. I had sore calves for a while. They're also expensive...I'd suggest REI, since you can return them even after they've been used.

I've used the Topo Adventure Terraventures, too (the original ones), and like them, too. The heel seems a bit snugger, and has worn a bit. Otherwise, little wear, but not a lot of miles on them, and not in rugged country. 3mm drop, I believe.

I used the green Superfeet for years, but have come to believe that they are detrimental, that they weaken your arches unless you have a medical reason for arch support. That was the case with me, at least, but everyone's feet are different.