Campman, be aware that if you are dry camping or boondocking, the furnace is the trailer's biggest power hog on the its battery.
that's why most of us dry campers/boondockers have at least two deep cycle batteries, along with a generator or solar system.
you'll run out of battery power way before you run out of propane.
if you have hookups, most of us use an ceramic heater to run and allow the trailer's furnace to supplement the ceramic heater.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC