Well, I guess I better chime in. We have owned and used two fifth-wheel trailers, both 28 ft long, the present one has a slide out that makes the living area really great. We go most every year to Colorado and camp in the Tiger Run RV resort just outside of Breckenridge. We have encountered -15 degrees weather and not had any problems because of our preparations.
First, we pull our 10,000 pound trailer with an extended cab Dodge 2500 with a Cummings Diesel engine and plug it's engine heater into 110 volts every night so it is ready to go in the morning.
The first trailer, a 1985 Jayco had an enclosed underbody, a necessity for winter camping, but the holding tanks had only a couple of inches of fiberglass insulation so I put a self sticking 110v/12v heating pad on the undersides of the tanks, they are available at Camping World. Next I rerouted a waterline from the water tank, which was under the sofa in the living area and not subject to freezing, because it ran a short piece inside the wall and was subject to freezing.
Our present trailer is a 1997 model and the water tank is in the basement and the holding tanks are in the shallow sub-basement underneath. The bottom is enclosed too and it has the holding tanks in it and is heated by a duct from the gas furnace and we had no problem of it freezing up. Whereas we could use an electric heater and be OK in our previous trailer we now have to heat with propane. But all in all it isn't that expensive and keeps the trailer warmer than an electric heater.
In the basement where the water tank is I have an 110volt outlet and I hooked up a light socket I could plug in, and when it gets real cold I can put either a 100watt or a 300 watt bulb in it to keep it from freezing, I never needed the 300w bulb and very seldom used the light bulbs at all.
I installed an indoor/outdoor thermometer on the inside and routed the outdoor sensor to the basement so I can check the temperature there at any time from inside.
During the stay for three weeks at 6000+ ft elevation in Summit county I do not use any antfreeze (the pink stuff really tastes sickly sweet even when diluted). Do not let any hoses hooked up or they will be ruined. Work out of your water tank and when it gets low, fill it and drain your water hose right away, the same with your sewer hose, dump and drain it and put it away, if not, you will have a stiff broken mess of wires and plastic.
I have storm windows that attach from the inside over all the windows, also on the old trailer, almost a must for winter camping. If your trailer or motor home does not have them, consider those plastic shrink-wrap ones.
Driving in skiing season has had it's moments but nothing serious ever happened, justy stay cool.
Anything else I can help you with just let me know...