As DMM digs the decline, then this adds to the stockpile material.  Some of the decline is waste material and some is low grade ore.  DMM hauls the waste away and processes the low grade ore it finds when digging the decline.  This is my understanding.

 

So DMM will continue to have stockpile material as long as DMM is digging the decline.  BUT, once DMM has 3 good veins exposed in the NW, Center, and SE of the Cabo Main Decline, then DMM really has no good reason to continue to dig the decline, and hence less stockpile material.