I can't believe what a controversial thread I started! I told my husband not to feel too bad that he didn't know about the C02, because it's obviously not known by many and, in fact, is debated as truth by many. He says it makes perfect sense, though. And he said this explains why he sees tires being filled with pumps at the Tour de France. He could never figure out why they wouldn't just use an air compressor, which would be so much quicker.

We, too, fill our tires before every ride. And this would explain why dh never realized the C02 had leaked so much. He just pumped it no matter what. I agree that different tubes, tires and the weather may account for the C02 leaking faster or slower. I think the "18 hour" thing the LBS guy said was just a number he threw out to say you can ride quite a while, but it won't last forever. He wasn't being specific.