Coupling caps,where necessary and properly biased on, are never charged and discharged, they are simply more charged or less charged, the voltage at the input never crosses zero.
Gas mileage. Ask yourself how important it is to pay $5000 for example to improve your gas mileage 10 miles per gallon. That is where miles per gallon is misleading. If you are now getting 40 miles per gallon, the improvement to 50 mpg saves all of 0.5 gallons per hundred miles, big deal. If however if your giant two story high Winnibagle is now getting 5 miles per gallon and you improve it to 15 miles per gallon, that same 10 mpg improvement, you save 13 and 1/3 gallons per hundred miles. Really honest big deal.
Go ahead, plot it out on graph paper, miles per gallon vs: gallons per hundred miles. Eye opening little exponential curve will appear.
Regards,
Frank Van Alstine
P.S. I just tried the ultimate coupling capacitor listening experiment in one of our new pieces of gear that is so DC stable that we could actually remove the output coupling cap if we desired. The listening test of output cap vs: zero ohm jumper yielded no significant musical difference. We will leave the cap in to protect the user and equipment downstream from possible DC output in the rare event of a component failure upstream. Of course if a "better sounding" coupling cap actually sounded nicer than no cap at all, then that would be really interesting and hard to explain, assuming stability was maintained.