Suppose my grinder's hopper contains beans roasted 14 days ago, and the hopper is almost empty; suppose further that I have a full bag of 5-day-old beans, ready to go.
If the new beans are added to the hopper on top of the old beans, then there will be an abrupt change to the coffee's "dial in" once the transition between the old and new beans is reached. This is a drawback in the commercial setting; it would be hard to keep track of where the transition is, so some customers could receive improperly dialed espresso.
The dial setting will also be affected if I wait until the hopper is completely empty; the grinder will not grind consistently if the hopper is underfull.
The final option I can think of is throwing away the old coffee beans to make way for the new ones. This seems to be a waste of money. Any tips?