Unpredictable mint time

Statistically speaking, the time to mint an x-bit stamp is highly  
unpredictable.  On average, you can mint an x-bit every 2^x/s seconds  
(where s = hashes/second), but the actual duration commonly ranges  
from barely any time at all, to 2-3 times the average mint time.

Minting *eight* stamps of postage x-3 would correspond to the same  
average amount of work, but, statistically speaking, would be *much*  
more consistent.  Having to wait unpredictable times for stamps to be  
generated is annoying.

It's also only eight times the data transfer cost, so not a big deal.

Thoughts?