we've had a good millennium for humans
40,000 years is 40 chances at other good milleniums occurring
Where cultures weren't using metals as the primary basis of infrastructure, there wouldn't be much evidence remaining of those cultures. Add in glaciers and everything is ground up, except in caves.
Or 300 chances! First homo sapiens was born around 300k years ago, and their culture rose and declined many times in many places. Around 40k years ago it did start to "monotonically accumulate" though.
See e.g. https://pmc.ncbi.nlm.nih.gov/articles/PMC3049097/
We’re so young. 40 millennium is honestly nothing on universal timescales.
But it is on civilizational timescales, that’s the point
Ensuring sentience survives heat death of the universe would be a marvelously unifying goal.