Tynwald, the Isle of Man's parliament, has operated continuously for over 1000 years

The Tynwald evolved from a jury into a legislature, didn't admit its first elected member until 1866, its first few hundred years of existence are assumed rather than documented, and actual power resided with a mixture of kings (most of whom were also kings of other places or answered to kings in other places) for most of its existence. So not an ideal example :)

How much of that time did it spend fully sovereign over its territory? I'd love to learn otherwise, but my impression is that it has mostly been under the shadow of England, and the pressures of a government under those circumstances are not comparable to those for, frankly, one that's more responsible for its destiny as a starship crew would be. I bet you can find lots of long-running tiny local governments with very little power, both dominated and protected by a string of larger, more powerful, but more volatile governments.

How's their space program coming along ;p pretty spacious place, ach!