I think that is hard to say; there are so many variable. We've got two 30's on our trailer and we rarely get into the second bottle for the whole year. But, if you are at high elevation with extended cold; using the furnace a lot; it surely won't last that long. We did one mountain trip where it was extremely cold. We got about 2 weeks out of one 30lb tank. If you have 2 tanks, it's not a big deal. Just switch to the other tank and fill the empty at your next convenience. Have fun!
2012 F150 FX4 Ecoboost, 2016 Surveyor 274BHS
2003 Yamaha FJR1300, Demco Premiere Slider
1969 John Deere 1020, 1940 Ford 9N, 1948 Ford 8N
Jonsered 535, Can of WD-40, Duct Tape
Red Green coffee mugs