Do unused cold packs expire

Answer 1

In short yes they do expire.

The timing varies depending on the manufacturer. If the pack appears yellow in color most likely it will not work to its original standards. It may not get as cold or may not stay cold for as long. The further from white the color is the less it is going to work properly.

Answer 2

Technically no they don't. However the chemicals can break down and the packaging can deteriorate. I would replace them every couple of years.