I was trying to get a CNG car in California for a while and ran into the issue that the model I wanted was old enough that almost all of them had expired or near expired CNG tanks, the labor for replacement would be very expensive, but that really didn't matter, because new tanks for that vehicle were nearly impossible to find. It's not great that they're exploding, but turning into a pumpkin 15 years after tank manufacture really kills the utility. (Maybe it's easier to replace on cars other than crown vics though)