pods have 2 things that expire: the internal battery and the guarantee of sterility. kept long enough, you could compromise one, the other, or both.
medical devices such as a pod have packaging, that packaging no matter how good it is, cannot sustain sterility forever. accelerated testing for sterility in controlled environments gives the manufacturer decay rates so they can see how long it is on average that the package remains sterile… by either carbon sampling or actual biological growth testing - then they “pick” a shorter period so they can have 99.9999 or 99.99999 (one out of 10,000 which is crappy, or 1 of 100,000 or even 1 out of 1 million) confidence they can guarantee sterility.
it is exactly the same with the silver oxide batteries inside each and every pod, except it’s not sterility it’s battery life.
so if you keep long storage… then you have watch that expiry and use your best judgement.