Personally I think auto-deleting data is a very bad idea - kind of burning the library of Alexandria. Not all data is valuable on its own however in context and with lots of points in data this brings back a picture of a civilisation.
In thousand years the issue of PII now is irrelevant. However someone looking for ancestors might just get lucky to know his foreforeforefather if that record still exist in some retrievable form of which we today think it is irrelevant.

The Sumerians pretty much had the same approach to their clay tablets. Good for some time, then break up and use as old tiles for the roof maybe.
Only reason we know of their accounting are a few of these clay tablets which allowed us to decipher their language.