Having worked in the food industry with businesses that comply with FDA protocols I’m aware that often shelflife labelling is based on a decision process that does involve the legal requirement to nominate some sort of date in addition to accelerated plus retained sample testing which both allow that the item may not be stored ideally during whatever shelflife is given.
In that industry shelflife extensions occur but more so for ingredients and intermediates than finished saleable products (the latter is often just a marketing decision). The better operators who are FDA compliant have processes to evaluate these items on a case by case basis and then approve a decision to extend, usually with documentation and/or relabelling that indicates both new shelflife and that an extension was given.

Is there a similar process within the pharmaceutical industry? Alternatively, how do we know that the drug involved is still known to be safe/effective rather than something that slipped through due to a human error?