For long term storage I would repackage them in glass with sealed lids. As for just ‘how long are they safe to eat’, I wouldn’t take the expiration too seriously - using your best judgement. Those expiration dates are probably written by lawyers to protect the food companies.
Having worked in the industry I can tell you that all food and pharma dates are only what has been tested to. Companies will not test out further because: 1) There is no payback for them to do so as vast majority of product is used within that timeframe and 2) They are only required to test what they claim.
So if 90% of their product is off the shelf and used by 3 months they will only test out to 3 times that timeframe (9 months). Then claim the something shorter than the testing (say 6 months) in order to provide themselves a safety margin.
Same thing is true of pharma efficacy - which is why I don’t throw away any unused antibiotics. Just keep them in a cool dry location out of sunlight.
Re Expiration dates:
ThankQ for that expert info. Love FReeQs vast knowledge!
The military has tested many pharmaceutical drugs to long past their expiration dates and found them still efficacious; I think that I have a copy of that study. I have practiced that timing for drug storage for some time. With this dock strike FReepers should try to hoard some critical meds that they depend upon such as insulin. This is no light problem issue.
“which is why I don’t throw away any unused antibiotics.”
That works with the ‘cillins and ‘zoles but the ‘cyclines gain toxicity over time IIRC…