While this is true, I don't think it is so much a matter of the sneaky drug companies forcing you to buy more medicine before you really have to. Remember, if it expires before they can sell it, they are the ones who take the hit.

It is a mater of practicality. If you are developing a new medicine, are you going to wait around an extra ten years before going to market so that some survivalist will be happy about the expiration date? No, you figure out how long of a shelf life you need to get the product to the consumer and give him a reasonable time to consume it, then test and certify that.