LPG holds less energy than gasoline, so you should expect greater consumption or less equivalent power output per gallon. Dry camping for three days this past weekend in the mountains with the heat left running and generator getting run two hours each day emptied about half of a 30 lb LPG cylinder (my Arctic Fox has two 30 lb tanks).
There are plenty of places that refill LPG and even smartphone apps that will help you locate the best prices. If you cannot find a refill location, there are plenty of locations that sell or exchange prefilled 20 lb cylinders (yes, 20 lb cylinders fit in my 30 lb location).
On long boon dock trips where we don't plan to head back into town, I usually have my enclosed trailer in tow that carries an additional 100 lbs of LPG. We use these tanks for fire pits and outdoor stoves, but also have the reserve capacity if we need more than 60 lbs of LPG in the TC.
