I just read John Glubb's - The Fate of Empires. Available in downloadable pdf from many locations on the interwebz..

A quick read. Simple, 27 pages, finds a pattern, in a very limited sample of 12 empires over the last almost 3 thousand years.

TLDR: After 250 years, yer toast. Vigorous expansion, growth, blossom, decay, collapse. Over, and over, and over again.

Made sense to my pea-sized in brain, as a kinda framework for a watch tower from which to watch the unraveling.