The author is ignorant of physics. Maybe the movement of electrons were expended, but electrodes tend to be more robust. They're not measured in gallons, either, but why ruin a perfectly good, albiet innaccurate, turn of expression.
Limbaugh himself has picked up on this, with his famous quips referring to his listeners as "mind-numbed robots."
The author is ignorant of Limbaugh's actual quotes. It's not his listeners he calls "mind-numbed robots."
The ones in some Xerox copiers tend to need replacing fairly often if the volume of printing is high. They're not cheap.