I did have a cord lock slip failure at about 280 miles, but I'm not sure that I didn't hang the lace on something.  Maybe it was just a poor knot.

Almost none of this distance was done of anything like a paved surface.  I generally walk mountain biking trails in my area, which are hands down more difficult footing than 90% of any of the mountain hiking trails I've been on.  I find it good "foot work"  for rock-hopping on portage trails.  Rocks here are not generally slippery like granite, but occasional scree areas can produce a similar effect.  I then sometimes mix in a couple of equestrian trails, which are mostly like walking on a beach with loose sand.  Five miles of that can be a bit of a work out, even without a load (its a bit like wading a stream for a mile).

dd