All sort of things done a thousand years ago still shape how we live today:
* https://en.wikipedia.org/wiki/Magna_Carta
* https://www.goodreads.com/en/book/show/2187985.The_Origins_o...
* https://www.goodreads.com/book/show/3624887-the-medieval-ori...
Who knows what the actions of a single, seemingly inconsequential, individual could trigger:
We have a bunch of family photos that were preserved for a few generations. It sucks, many of them we know who they are, the most are lost to time and the death of memory.
Pictures without the context are just images of dead people. With the story, they are priceless memories.
I don't disagree that a few things that happen today will be of consequence. I disagree that any single source of that data needs to last for a thousand years in isolation.
There are, I'm sure, one or two examples of thousand+ year old primary sources revealing otherwise lost information that was still relevant in some way. I suspect not many, other than as datum for academics to ponder.
Important information has always survived by copying.
> Dating from the 3rd century BCE to the 1st century CE, the Dead Sea Scrolls include the oldest surviving manuscripts of entire books later included in the various Jewish and Christian biblical canons, including deuterocanonical manuscripts from late Second Temple Judaism, as well as extrabiblical books. As such, they cast new light on the emergence of Rabbinic Judaism and of Christianity, and their relationship with Jewish religious traditions.
One could similarly imagine a set of M-Discs from today that would be rediscovered 1000 years from now that could prove similarly useful to the people of the future thanks to data on them that has been preserved unaltered since today until then on that set of M-Discs.