I am afraid my trekking shoes met their match in Nicaragua.  I managed to wear off the outside portion of both heels while using my feet to steer and brake on my boarding descent of Cerro Negro.  Even though the entire run was probably just over a minute, the scree was so abrasive that it removed a major chunk of Vibram sole from each shoe. This pair of trekkers has served me well and I will be sad to retire them.  By my estimate, they have visited more than half the US states and well over a dozen countries.