New tanks have to be inspected every 12 years, and once you change the valves you have to have the tank inspected every 5 years. The steel tank's replacement valves are so expensive that, with the inspection cost, it is hardly worth chaging the valve. It is best to buy new tanks.
With the aluminum tanks that is another story. The guide lines for inspections are the same but they are so much nicer. The replacement valves for the aluminum tanks vs the steel tanks are differant. They look about the same but the aluminum tank valves are a little longer. The right valve for the right bottle is a serious matter. The Overfill Protection Devise will not work properly in the wrong tank.
We do carry both replacement valves 30lb and 40 lb at Out-of-Doors Mart MORE Airstream Parts on-line than anyone!!! And we accept PayPal.
30 lb OPD Valve for Aluminum bottles SKU8355 - $28.95 : ODMRV , Out-of-Doors Mart
40 lb OPD Valve for Aluminum bottles SKU8356 - $29.95 : ODMRV , Out-of-Doors Mart
These replacment valves do interface with the new hand tighten hoses so it makes little since to not get them also. It sure beats getting in the tool box every time you need to refill your bottles to get a wrench.
I had a guy share with me one time that he changed the valves himself. He said ,once his bottle was empty he got some cloth and wrapped the gas bottle so he would not scratch it. He got a large chain and wraped it around the bottle then put the chain into the vise. After cutting the hose off the brass fitting of his old hoses he screwed it back into the bottle. Then he used a large pair of slip pliers to screw out the old valve by grabing a hold of the brass fitting. He then used the same method to put it back in. Mind you, I did not see this done but do know he did not return the gas bottles valves.
I have also heard of where the gas companies who inspect the Gas Bottles do have the tool to change the new valves but do not carry the aluminum tank valves.