I bought these Nike Pegasus 28 running/walking shoes back around May 1st or 2nd. According to my iPhone pedometer, I've walked just under 175 miles since then. Looks like I'll be replacing them much sooner than the 4-5 months or 500 miles that I had planned. I walk on asphalt mostly at a brisk pace (and a few muddier areas at the edge of the track, thus the dried mud patch on my right shoe sole), but I didn't realize just how quickly I was wearing the tread out.
Luckily, I have a pair of Saucony Shadow Genesis to wear until I can afford a new pair (maybe around my birthday in a little over three weeks?), but it is depressing to see just how quickly I wore these down, as these were some comfortable walking shoes (and I rarely wore them outside of the track).