I wouldn't dismiss tank exchanges out of hand. Yes, you may get less propane, but you will always (or at least you're supposed to) get a tank that has been inspected, refurbished, and the old ones are taken out of circulation (they are date stamped). So there is SOME value to doing it that way.
I have 2 or 3 places within a couple miles that will fill my tanks. And we've used our trailer a total of 6 times and have not run our primary 30 lb tank dry yet; almost empty on the primary tank as of our last trip. It would have to be a pretty serious trip to run a tank empty unexpectedly, although I did have a pigtail start leaking on me, so it could happen...
2014 Jay Flight 28 BHBE
2015 RAM 2500 6.4L HEMI, Tradesman 4x4, 3.73
Blue Ox SwayPro (BXW 1503)
Upgraded from an REI internal frame backpack and a Eureka 1/2 dome tent!