Where i live it gets into the 20's but only at times as you know. I only winterize if i don't plan to use it all winter. Trailer is under a roof at my home with a small electric heater plugged in at it's low setting.
If 20 degree weather with a strong east wind is predicted i turn on the rv furnace set at 50 to help for a few days or untill it warms a bit.
Probably goes through one 5 gal propane tank the entire winter.
It depends on your particular rig i'm sure. The one i have now has heated tanks so would be less of a problem i'm sure.
