[ogurechny]

I've been using an old Symbian phone with the same Class Not-That-Good SD card bought back then. In the early 2010s, I copied a lot of MP3 files and ebooks there, and used the camera to take photos occasionally. Then it was no longer used for music and other needs, and the files just rested there. After about 10 years, I've decided to play some music on the phone, and these tracks had a lot of skips and rattle. Images copied from the card showed a lot of damage, too. So when someone on the internet posts how SD cards are a cheap and compact long term storage, I am not impressed. You probably need to refresh all previously stored data with each monthly backup.

It should be mentioned that the phone board often gets warm during operation or battery charging, and the temperature is stated an important harmful factor in a different comment.

So if you have some old files on an old device, and assume that they are still there because their records in the file system still look fine, you might be surprised.