[fogice]

Database corruption is a real thing. Some people reboot their Kobo before plugging it into the computer to ensure that all the database stuff is properly closed before connecting to Calibre and transferring new books.

Sudden battery drain can also happen, likely after a new ebook is transferred to it. It even drains in sleep mode. I'm not positive the steps to stop this, but I find that deleting the books I just added, doing some reconversions on them, and reuploading them helps. So might a Kobo reboot.

Neither of these issues have anything to do with the age of your device.

At the moment, I have a personal policy to not add any new books a week before I go on vacation, to ensure that I don't have to deal with sudden issues.