Typical Power Station Lifespan?

So lets say for example I buy a Jackery 500. I know about the 500 charge cycles reduction to 80%. But if I want to use it for SHTF purposes and keep it charged to around 80% every few months, how long would it last on the shelf. I've seen comments that it has about a three year shelf life, but that seems way low. Could someone comment?

This thread has some links that might help you out: https://diysolarforum.com/threads/soc-degradation-of-lifepo4.13215