>>Do you wear them in that order, with the heavier wool on the outside of the oven bag? And the oven bag doesn't rip (I had small trash bags rip within a day!)?<<
Yeah, in that order. In really cold weather, I've tried bags right against my feet, but I just don't like the feel...even though I know they say VBLs should be worn right against the skin. My (non-scientific) experiments led me to just us as thin a sock as possible under the non-breathable layer.
I get a LOTS of miles (maybe 100 or 200? - not exactly sure) out of those oven bags. They're way stronger than grocery bags...and a good deal stronger than the bread bags I've tried. The only part that ever breaks is the seam, and it's never been a catastrophic break...just a small tear. I keep the seam under my foot (that's kinda the only way it fits on your foot), so water can't really rush in or anything.
This weekend, I removed the bags when I got back below snow line, and jogged out the last 10 miles or so. By the time I got back to my car, I had pumped out the residual moisture from my sweat, and my socks and shoes were 99.9% dry...and more importantly, they remained warm all weekend. The same could not be said for my friend, who was wearing Gore-Tex runners.