I do the same as echidna. You can get a box of CO2 cartridges at Walmart that amounts to about $.50 a cartridge, so make sure you get an inflator that takes the unthreaded cartridges. Also, my next pump will be a Topeak Morph, as one time when I had a problematic change on my mountain bike, a passing biker pumped my tire in nothing flat with a mtn. morph he carried in his Camelbak. It was lightweight, unfolded to work like a floor pump, and was very efficient. However, I live in the Phoenix area, and using any pump in the summer sun is nasty, so I always carry several cartridges of CO2 in the saddlebag.