As a chemist, I will go ahead and inform you confidently that Potassium Iodide in a dry place will outlast you by a significant margin. It’s very chemically stable.
Probably to account for people who won’t store it properly, degradation of the packaging material, etc.
For example, if you store your blister pack of KI on a sunny shelf in your bathroom, UV rays eventually weaken the plastic packaging, cracks develop in the plastic letting in water vapor from your shower, and a stray mold space makes its way in as well and eventually you end up with mold growing on your pills. The KI itself may still be perfectly fine and able to do its job, but that mold might make you sick.
As a chemist, I will go ahead and inform you confidently that Potassium Iodide in a dry place will outlast you by a significant margin. It’s very chemically stable.
What’s the date for, then?
They’re required to put some date, and nobody wants to pay for a 50-year medical study to show what chemists already know: KI will still be KI.
Regulation compliance probably
Probably to account for people who won’t store it properly, degradation of the packaging material, etc.
For example, if you store your blister pack of KI on a sunny shelf in your bathroom, UV rays eventually weaken the plastic packaging, cracks develop in the plastic letting in water vapor from your shower, and a stray mold space makes its way in as well and eventually you end up with mold growing on your pills. The KI itself may still be perfectly fine and able to do its job, but that mold might make you sick.