It's poetic how this happens throughout the course of history, it rhymes often. No empire on this earth lasts forever.
It happens with the Romans, it happened with the Spanish, the French, the Dutch, the Portuguese, and the British Empires. I have a funny feeling that the next domino to fall will be the American Empire, and it will be a long and bloody fall if the people, especially those in charge, refuse to learn from history.
There are two ways empires fall. One, they relinquish their colonial practices, allow colonies to break away from the mother country, and the nations maintain their identity. Two, they refuse to relinquish their colonialist ways, and try to drag others down with them and the country collapses from the inside and they break into multiple nation-states.
Only time will tell which path America will tread down.
At the very least, we are currently seeing the end of the America-centric hegemony that came out of the last World War and especially out of the end of the Cold War, and frankly, on the global scale, that's probably a good thing. Though there are the worst kind of idiots at the helm, the unipolar America-centric network of global slavery is coming apart and ultimately this will be a good thing, though those of us who are along for the ride are in for a bumpy one.
Howdy.
This idea about falling empires or "civilization after some point of culmination" has occurred to me more than once in recent times. You are not alone. The idea of watching the show unfold from the window at the Restaurant at the End of the Universe has come with that as well.
Cheers.
Restaurant at the End of the Universe eh? You a follower of Slatribartfast?