Does a Balance 210 have to remain plugged in?

I have a spare Balance 210 HW4. Does this have to remain plugged in or else fear that a bios battery will die and it won’t boot up in the future? Wondering if I can store it in the box or if I need to leave it plugged in to have it as a backup.

Well, I’m leaving it plugged in for now.

Wasn’t sure if it was only the balance routers with the lcd screen that have an issue if a bios battery dies, or all peplink/pepwave routers?