As a newbie diver who goes through air like the congress goes through money, I find this discussion heartening. Did a nice dive the other day on a couple of wrecks, and I hit the boat with 500 PSI... and my buddy had about 1100 left. He was very gracious about it, but I still felt a little bit like a dork. It was a club dive, so at least we didn't pay for the air or the boat (other than club dues and a tip to the captain)...