I came to share a similar experience running the numbers for a tier 1 IP carrier customer service desk.<p>Per call mixed FIFO&#x2F;LIFO also gives you a good feel for how technical situations are progressing, and still depletes the older queue entries.  Any given center can usually be dialed in, by changing the ratio off the top or the bottom of the stack for the next served.<p>I would imagine dynamic heuristics based on volume and delta volume&#x2F;period would greatly assist keeping the queues clean.