Earlier quoted context omitted.
There definitely can be human civilizations that last indefinitely, so long as we stop keeping all our eggs in one basket, planet-wise. Once we get humans living far enough apart that information about pandemics travels faster than pandemics do, then we should be largely invincible, barring suicide from ennui. The larger our sub-galactic civilization, the more resilient it becomes to things like total war, total poli…
So as long as we do what no society has ever done, society can last forever?
It's easily conceivable that 100 decades from now we could do this too.