Thanks for advice.No, not every year and not every location. From experience I know what I need to do to achieve "No N, P, K required" status.
I now only test in special situations such as some experiment I'm running or other special situation.
To get a baseline, in your case, I would probably mix samples from the containers and send that in for one test and mix samples from the 32 sq. ft bed and send that in as the second test sample. That should give you a good baseline starting point.
This site is very helpful