I think of this in terms of being a diabetic. I'm currently insulin dependent. Even with refrigeration, my supply would be intermittent or degraded in weeks. Without it, days. I will revert to metformin and other non-refrigerated pill types of blood glucose reducers, which should tack on a few months, or a couple of years. Basically, though, it's down to reducing carbs and increasing exercise and still facing a shortened life span, as many people will for various reasons when SHTF if it's pervasive and long-lasting.