Thanks for the informative post.
Are you saying you can transfer propane from a large tank to one of the smaller ones? If so, how do you do it? I have a couple of RV tanks that are past their expiration date, and they won’t refill them. I’d like to transfer propane into them from my newer tanks. I want the older tanks full in case of weather emergencies.
See if there is a propane wholesaler near you who can inspect and recertify them. Depending on your area, this may be possible. I can get 5-year recertification on my tanks and I have two that are more than five years beyond the original 12-year expiration (one tank is 19 years old, the other is 22). It comes down to the valve type generally, the older type won't get a recert due to safety reasons but newer valve types can be as long as the tank is in good shape and doesn't currently leak.
I refill my 20# tanks at Tractor Supply where they check the date on the tank. (They rust internally and the weakening cannot be seen from the outside)
If a tank is too old they will NOT refill it.
So I take it to Walmart where they do NOT check the date, but merely swap tanks with you. (I assume the refill company checks the date at it’s location.)
I get a newer tank for WAY less than buying a new one.