I have used my furnace every winter at my home base since 2010 and it works great. I have upgraded the thermostat to digital and I also use an external 150 gallon propane tank. I plumb it to the trailer via a copper line and hook it into the trailer plumbing after the trailer regulator since the external tank has a regulator. I did have the tank regulator checked for proper pressure prior to using it. This has worked well for me for 4 winters and buying propane that is delivered to me 100+ gallons at a time (gallons not pounds) is a lot cheaper and much easier than buying it 30 pounds at a time in the little tanks. I probably haven't filled my built in tanks more than a half dozen times in 4 years of full time use and I'm talking about a half dozen total, not for each tank. Now my propane usage isn't that little. This past winter was cold where I home base. I saw 8 degrees several mornings with the daily temp never getting above freezing. I was nice and toasty inside, but I burned a little over 200 gallons of propane over the entire winter.
I keep my fresh water tank full during the winter and operate off of it. I only hook up the water hose to fill the onboard tank when necessary. Otherwise the hose is drained and ready for use even if the outside temp is below freezing.
My home base is in central Alabama, but where I am now.
2006 GMC 2500HD CCSB 4x4 Duramax/Allison, Titan 52 gallon fuel tank, Prodigy Controller, B&W Companion Hitch
2010 Jayco Designer 35RLTS, Cummins/Onan RV QG 5500 EVAP, Progressive Industries EMS-PT50C, TST Systems 507 TPMS, RV Flex Armor Roof