Winter touring

Hi All, I have just returned from a 5 day trip and experienced  below zero temperatures. During this trip I changed over to Propane gas and found  a great difference, you need less gas to do the same job. I was using a 4.5 kg Butane in 2 days, is this unusual?  Also what is the best way to use the water heater, do you heat the water as you need it or do you leave it on continually? I was  using gas only without elect hook up as I was in forestery sites and we do like our comfort but is this gas usuage too much?