[yomly]

I would expect the chemistry to be characterised well enough to the point where you shouldn't need clinical tests to know it's degredation profile...

[EpicEng]

I don't know about that. There are variables beyond theoretical chemistry, like the packaging, the manufacturing process, etc.

I'm not anywhere near knowledgeable on pharma, but I worked on an FDA regulated medical device. If we made a claim, we had to test it. Knowing that e.g. every component in the machine was rated safe between temperatures X and Y did not mean that we didn't have to perform real environmental testing.

[ekianjo]

Regulations don't want you to rely on models.

[Kalium]

From what I read, current expiration dates are produced by the sort of actual testing I described.