The cited section of the regulation specifies the minimum number of batch samples from a refinery, which once created, must be maintained (twenty). The regulation does not specifically address the maximum amount of time that any particular sample must be maintained.
This was not considered to be an issue since the Agency assumed that refineries and importers produce or import a substantial amount of batches each year. Such parties would accrue the twenty batch minimum in relatively short order, so that they would effectively be able to dispose of any additional, older samples quickly.
This question indicates, however, that at least one refiner or importer handles less than a handful of batches each year, so that its batch samples might have to be retained for an extensive amount of time, such as between ten and twenty years. The Agency did not intend for refiners to be required to maintain sulfur samples for an excessive amount of time. We will address this issue through a future rulemaking.