[Frumious Bandersnatch]

Actually, the Byzantines were themselves, in great measure, responsible for their own fall. Their corruption was so endemic it gave rise to a new word to the lexicon - byzantine.

[Chancellor Palpatine]

For a bunch of corrupt and inept people, they managed to hang onto things from the 4th century to midway through the 15th century - over a thousand years of continuity, not even counting that it could claim the Roman continuity as well. That makes for over 1800 years of a civil government.