If your propane tank is over 12 years old you cannot refill it!
Propane tanks have a manufacturing date stamped on the handle, the tank can only be refilled for 12 years (after manufacture) unless it has been pressure tested and re-certified (the cost to re-certify is almost as much [or more] as buying a new tank).
If you use a Tank-Exchange program this will not affect you, as the Exchange Company ensures each tank is inspected. tested and certified. However, you pay a premium for the convenience of using tank exchange programs.
If your tank(s) is/are close to expiration and you think you will just exchange it one time to get a new tank from the Exchange Company, BE AWARE, some Exchange Companies have started to use proprietary valves and fill stations are not able to refill the exchange tanks. Obviously, the Exchange Company wants to lock you into using their exchange program.
So, check your tanks! The last thing you want is to be out on a trip, in need of propane, only to find out there is no way to get propane into your tank because it's certification has expired.
Happy Scamping !!!
PS: If your tank has expired, Please don't ask to have it filled one more time, the fines are HUGE for anyone filling an Expired Propane tank (as well they should be, people could die!)