Planted Tank Guru
Join Date: Jul 2010
Location: Huntington Beach, CA, USA
On the tanks I've dealt with, the certification is required every five years. I think that is a national standard. There should be a date stamped into the soft metal around the top curve of the tank. If you own the tank, yes, you will often have to pay to have it tested every five years or so. But if you own a tank and just take it to swap it at the same place, I find they are willing to cover the testing.
I am not in love with any tank and just swap but others have tanks that they really like and would not want to do that.
I look at the tank as a tool, hide it under the stand and go for the place that refills/swaps cheapest. For me, that is the welding gas supply. It may be worthwhile to call a few places to ask how they deal and what they charge for a tank. I find there is only about a dollar difference in 5 , 10 or 20 pounds as the gas is cheap but the labor is pretty much the same for all sizes. Your prices will likely be different.