I was not aware of the fact that password protected USB sticks have a limited lifespan. Since they are stored in a low humidity/room temperature with nearly no write/read activity I think they can last some time, but it's definitely good to be aware that they don't last forever. Thanks!
I should specify it applies to any kinds of USB sticks (and any storage device actually).
Consider replacing it every 5 - 10 years and having more than one backup solution (which you already done).