In a book series I'm hoping to write and publish, the fictional timeline covers a period of several centuries, with the key years being from 2275 - 2840. A key plot point of these books is a totalitarian culture called the "Centauri Alignment" (descended from a lost human colony in Alpha Centauri) that gains control of the Solar System following a ruinous invasion and war that sets all sides back economically and technologically. The Alignment controls the Solar System for almost six hundred years (i.e. the years indicated above). During this time, although they retain a significant amount of scientific knowledge and high technology, their culture is stagnant and petrified, with economic/technological progress being non-existent under a ruinous centrally-planned economy. My question is this: is it in fact, plausible under any circumstances for a culture to exist in such a state of stagnation, mismanagement, and oppression for such a long amount of time without collapse, given the relatively short life-spans of real-world totalitarian regimes such as Nazi Germany (12 years) or the Soviet Union? (74 years)? Does cultural longevity necessitate at least some form of ethical governance, or could more long-lasting methods of totalitarian control develop in the future? Thoughts would be appreciated.