Not True.. They always still work for me.
The problem in my opinion is, they won't stay backed up.
As soon as you turn it completely off and back on it goes to the newest update it was capable of getting.

Such as.. If you backed it up to a old 79.0.... And it was at 90.0....something. It will go back to that.
EVEN THOUGH it is EOL and can't get a NEW update.

They appear to be set for getting what ever the update is going to be the day they reach that date in history.