How do they measure the “loss of effectiveness”?
Not entirely off topic. I haven’t learned how to use multiple addresses. So...
Some use-by dates (probably the Epi-pen, as an example)are determined by the integrity of the sterile package barrier. We determined our labeling, in part, by ‘insulting’ packaging that had undergone accelerated ageing.
Basic microbiology techniques and statistics do the rest. We also ran Limulus amebocyte lysate assay tests on components and, if if time and budget allowed, other tests, too.
Accelerated and real-time aged devices and packages are gold - one tries to learn everything possible about the behavior of the components and differences between sterilization methods (gamma vis EtO, foe example)