Most doctor's will write a RX for a Conserving Regulator, that will only discharge the O2 when you breathe, prolonging the length of the tanks. Don't ever use the conserving regulator's at night though because you often breathe too shallow for it to register and discharge the O2. Like others have said, plan ahead for outings and trips. The Lost Miler also posted about buying a concentrator. I did look into that and they are way too expensive, but the reason why insurance companies don't buy one for you like they do with the Vest, is because O2 concentrators are prone to breakdown and need frequent repairs. So they prefer the rental method.