Steve, I would respectfully disagree that "there is no right or wrong here." I would say that my way, which is not to use the heat, is the wrong way in very cold temps, as bka correctly pointed out -- the water lines could freeze, unless you drain them. But when it is only in the 20s, it is probably a matter of personal choice. We like it cold, and we like to save our battery power so that we almost never have to run our generator.
Since we come from coastal southern California, where it is in the low 70s every day and low 60s every night, it is fun and different to sleep in a very cold room (in the low 40s or high 30s). Plus, we sleep better in the trailer than we do at home -- at home, we never get to use our down comforter. It was a wedding gift in the late 1970s, and we still have it, and we are finally getting to use it!
Just to show you how crazy we really are, this shot was taken in Yellowstone when the outside temp was a little below 20 -- this is not a trick shot -- the cord on the coffeemaker froze in this position, inside the cabinet:
And if you want to join the Siberian Campers Club, I recommend a Russian fur hat -- this one looks like mink, but it is actually sheared lamb's wool. It will keep your head warm, even if (like Gary and me) you don't have much hair. The temp at the breakfast table was 38 degrees when this shot was taken, in the Gros Ventre National Forest in late October -- the window behind DW is covered in ice: