We have had no problems when we run our heater, we don't keep it 80 inside either. It usually only kicks on a few times during the night, nothing crazy.
Since we have an outlet for the RV at the house, we'll just dewinterize a day before we plan on leaving and turn on the furnace and/or separate electric heater and set them to around 60F. Turn the fridge/tank heat on and start loading up. Then we just run the furnace while on the road. We also run the generator from time to time.
Over Thanksgiving, while down in Oklahoma during that ice storm, we didn't have any issues with this setup. We also just bought a little electric heater from Walmart for $10, and it works nicely. So if you don't want to use propane, you can just run the generator for electric heat. Don't be afraid of that Onan genny. Go ahead and run her 8 hours or whatever you need. She'll take the abuse. Just check oil level and you'll be good. Have a safe trip!
Just a word of warning. Some of the RV's have heat ducts to feed areas that can freeze the water lines. If you don't run the heat at least 45 deg. you could have freezing. You can use elec. heaters, just open cabinet doors to get heat in. I would run unit heat at 60 while asleep.
The generator, at full load, should use 1.5g or less of fuel per hour. If you take an eight hour overnight break, I'd expect no more than 10 gallons of fuel, costing less than $20 (US) now. That's less than an RV park and will let you run an electric heater or two. Of course, tihs doesn't include maintenance costs for the generator.
Our 33' 2011 Georgetown with its two 12V house batteries can't make it overnight when it's cold, the furnace is running, and we're boondocking. It usually takes around six hours to drain the batteries to the point where the propane/CO alarm activates as the furnace kicks on because it detects low battery voltage. My solution, a third house battery, will let us go overnight without problems.
When the house batteries need replacing, I'm switching to two 6V golf cart batteries and will be installing a multi-stage converter. The current third house battery will be kept and used only for its intended purpose, something not related to the RV.
We travel from WI to FL for the Christmas break. We winterize or unwinterize around Nashville. It's about as far North as I could find RV parks open year round with the water on. There are quite a few right off I24, I40, or I65. The basic ones only charge $20-$25 per night for FHU. I crank the electric heaters and use their water to fill or drain the tanks. It works good being about half way to Florida. Have fun.
Linear Mode
