We normally look for a Tractor Supply to refill our tanks when on the road. I recently took two bottles to our local TS store and they would not fill them! "Out of Date" the guy said.
So 2 miles up the road was a WM Supercenter. This was the first time for me to do the exchange switch. They charged $17 for each 20lb tank. Had to go inside to pay, and back outside to wait for someone. After the gal did the switch, I asked if she wanted to see my receipt. Not necessary, she said, you look honest. 