2 questions: He's using Red Line what? 20-50 or 10-60 motorcycle oil or 5-20 auto oil?
Second, how far down does he let it go before he tosses in the next quart? Pumping oil out into the air cleaner usually slows down or stops when the level is in the cross hatched area, half way between full and add one quart. If the level keeps going down below the add 1 quart line, he has a more serious problem. If he has coasted down a long hill and then adds throttle, is there a puff of blue smoke then? Does he get a puff of blue smoke on start up? Either of those would suggest valve stem seals. What do the exhaust tips look like, and how do the plugs look when he pulls them out? If it is running that much oil through the combustion chambers, I can't believe he doesn't need to change plugs almost weekly. If the plugs look normal, has he checked the transmission and primary to see if they are receiving the oil disappearing from the crank case?