[pct-l] how do running shoes tend to die, and when?

[greg mushial]

For my (what proved to be an aborted attemp on Section O) I gave up on the 
boots and went with running shoes. In this case, the bottom of the line 
Nike's - $29.95 at Target on sale. Before heading out on O I put 60ish miles 
on them on the local fire trails/roads; on O I added another 35-40; and 
since then, another 300ish again on the fire trails. Clearly at this point 
they'd nolonger be confused with new shoes - they're more northern calif red 
clay dust red than their original blue and grey; the foodbeds have taking a 
nice imprint of my foot, ie, they fit my feet well, are super comfortable 
(and clearly one would have no problems finding them in a dark room - just 
follow your nose). But I'm wondering is: in reading the various trail 
journals it seems thru's are replacing their shoes every 500 miles +/- [yes 
they're carrying a pack, but mine only added 15% to the total weight the 
shoes would see]..  how do the shoes tend break down? Stiches blow out? 
Bottoms wear out? I've read about some thru's limping into the next resupply 
with their shoes more duct-tape than shoes etc) I'm wondering if by buying 
the bottom of the line shoe, and being very basic shoes, ie, real laces 
through real eyelets, ie, no super duper space age gonzo light stiff... 
they're actually more robust than the upper end shoes? At this point, if 
they continue to hold up like they are currently, I'm inclined to try to 
find a couple more pairs, and used them for next year's hoped for thru.

many thanks - TheDuck