Ed,
I think you are correct on the unlimited retesting, but I know there is a
descending retest span and I think the first is 12 years or maybe 10 years,
then five thereafter. Check your tank and see if there are two previous
dates acending from your last date. It may be different for RV tanks, or
different for your local area ordinances. I know TX is longer span than CA
like the emission requirements are different for CA motor vehicles. Here we
still require a drivers license and an ability to read and see when drunk.
Of course this is a selective enforcement.
-Eddie-