I just got the Filson 257 with the neat pricematch/bing cashback trick, but I'm curious as to whether or not anyone has any experience with the wear and tear on the bottom of the bag. I know its a heavy-duty waxed canvas (believe the 257 has two layers of canvas on the bottom), but even after a few years of daily use I'd imagine that wear and tear would take its toll and I'm wondering how long it takes until the the first (or even the second) layer of the bag would start...