As an “experiment” I tried using my expired insulin that was opened 1 year ago. It was opened and travelled unrefrigerated for about 8 hrs in ~68F, and subsequently refrigerated in an ordinary refrigerator. I’ve been using this same bottle for quite some time without any ill effects (insulin impotency). I do keep the vial refrigerated at all times.
I read somewhere else that insulin can last longer than the expiration date - yes, my experiment has confirmed this. Even after opening, it can last beyond 28 days - yes I confirmed this too.
So…I do think that the big pharma would prefer that we discard usable insulin. While this is not intended to be medical advice, but rather my own opinion and experience, I wanted to share with the group. It made me sad to think that I discarded perfectly good insulin because it had expired, or had been opened for 30 days 
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