- that is not quite true regarding the pharma companies. The various governments require stability tests, where the drugs are stored for a given period of time (i.e. 1 or 2 years) in the type of conditions that might be expected - usually with a lot of temperature and humidity variations. After this storage
period they are analyzed for physical and chemical deterioration. If no deterioration has occurred then they get approved for a shelf life of however long they were tested for, this is done by a national regulatory agency such as the FDA. So even though the manufacturer knows from their own tests that the drug might have a real shelf life of over 10 years they cannot label the product with any expiration date other than what the government
mandates. For this reason you will see various shelf lifes for the same product in different countries. Many countries even require their own stability tests and won't recognize any tests done overseas - Japan
being a typical example. In Japan
they require that all foreign pharmaceuticals be re-tested prior to be approved for use in the Japanese marketplace. Even such products as Aspirin had to go through this expensive and time-consuming process.