Propane... NOT a problem... Assuming you are not running the furnace it will last you well over a month.. Running the furnace.. A month is not out of line depending on the size of the RV and the size of the tanks, 3 months not out of line, I fill (usually) three times a year.
Batteries: thats another matter: ONE night with heat if you are lucky, perhaps 12 hours if not using heat. So you will need to recharge daily. At least six hours to re-charge depending on battery/converter ratios, Proper ratio is converter = (Battery)*0.3 (Battery 20 hour amp hour rate or C/20 rate).
This is for 3-stage SMART converters.. NOT the Parallex 7300