Do cots expire?

I'm curious, do cots actually have an expiration date? I've heard of various financial instruments and assets that have a shelf life, but I'm not sure if the same applies to cots. Could you please clarify if there's a specific time frame after which cots become invalid or cease to exist? It would be great if you could provide some insight into this matter, as I'm trying to better understand the nuances of financial terminology and concepts.