Tangential to this issue and an interesting sidebar is the issue of whether the insulin directly issued from the manufacturing source is always at 100% potency. From a DiabetesMine column published in the last year or so:
They randomly picked up 18 vials of insulin and stored them in a research lab at the appropriate temperatures, before discovering that the concentrations weren’t adequate. Insulin vials and cartridges are required by the FDA to contain 95 U/ml of insulin when they’re sent out by the manufacturer. Regulators also require proper handling and temperatures in order to maintain the quality.
But when Carter and his team examined the insulin they’d purchased, the vials ranged from 13.9 to 94.2 U/ml, with a mean of 40.2 U/ml. No vial was at the minimum FDA-required standard of 95 U/ml.
As if we who try to do this incredible metabolic balancing act don’t have a hard enough job and then find out that the central tool we’re using and thinking contains 100 units per mL only contains 40.2 units per mL! That’s not funny. 
According to the article, the Diabetes Technology Society was supposed to do some follow up but I’ve not seen it covered anywhere. As expected, the Pharma-financed ADA dismissed this news.
I wonder how careful the insulin supply chain manages the temperature of insulin?