I have camped in some very cold weather in Idaho and never turned on my tank heaters, with that said I do pour RV antifreeze in each tank to ensure the valve part hanging outside the under belly covering doesn't freeze. My thoughts are that my tank heaters were more of a sales item then an actual necessity.
Jake my sidekick (yellow Lab) 10/04 - 05/20
2017 RAM 2500 CC 4X4 Cummins Diesel
2016 Flagstaff 26 FKWS
AF&AM & El Korah Shrine of Idaho