I typically refill all my tanks. BUT I used to often stay for a month or more in a small town in GA that had no place that would refill a 20LB tank. We could only do tank swaps. It was weird but not a big deal since I have always had one tank that was a "swap" tank (one that I typically would either refill or swap). I ended up with two swapped tanks and two owned tanks during the years that I was going there. I could refill all my tanks when I went back home.
I currently have "several" 20LB tanks of which two are "swappers" (Tanks that I have gotten at whichever tank swap outfit is locally). I always paint my owned tanks a very different colour (Rustoleum light turquoise for the last 10 years) and the "swappers" get painted white so I can easily and quickly tell which I will swap (I have gotten old rusty tanks at swaps). I treat the swappers like my tanks in that I keep them clean, rust free and paint them every few years as needed. I tend to remove the wrapper as it holds moisture which accelerates rust. I don't even worry about the age of my turquoise tanks. They are in such good condition that the tank fillers always say how good and clean they are. I keep the swappers because I don't always keep all my tanks filled. I have found a few times when I needed to swap a tank out because I ran out of LP when the tank fill is closed.
The truck camper has one swapper and one owned tank. I figured the tank that came with the camper could be the swapper and I added one of my tanks to the camper when I set up a dual tank system.