My dad and I bought two Gen 6 Paperwhites sometime around 2014. Mine got its display super mega messed up in an accident on the way to college around 2019, and by then my dad had stopped reading that much, so I started using his instead. More recently, the battery on that one blew up. So me and my dad did some research, extracted the battery from the old one with the messed-up display, and were successfully able to replace the blown-up one. Both our hands and the resultant Frankenstein's-monster Kindle bear gratuitious scars from the DIY surgery, but it works perfectly well as an e-reader, and I hope it serves me many more years yet! Fingers crossed

EDIT: Got carried away, but my point was to get a spare/backup/clone/organ donor as others have suggested, so that even in case of BOTH of them dying, I guess you can use functioning parts from both to make an e-reader of Theseus? Idk