As Mtracer and a few others have said, my reluctance (if I ever exhaust my current supply of CO2s) is the battery. Not if a full charge will replace the pfffft of two CO2... if the full charge will be there when I finally need it. I mean, I suppose the inflator could be number 8 on the list of things that have to be charged up to leave the garage, e.g. Di2, computer, phone, tail light, headlight, power meter, HR strap...