Been using, and enjoying, the DC cartos in the UFS but wondering... how long does one last most people? It's been a week for me and still going fine (draw starting to get a little harder, but that could just be the UFS needing a little cleaning), I do about a tank a day. Running at 3.7v, haven't gotten around to getting some 3.0v batts to try out 6v as most people suggest.