They're lasting 800 miles.  The mane changes this year were reducing the rear lace to 10 passes of string & gluing the rear lace to the sole.  The most time consuming part is cutting all the materials.  Gluing 2 pairs takes 4 days because of the number of clamps.  

The lifespan has been limited by large wear areas in the middle of the sole which would require a completely new sole.