Is it possible to create an AI that will last a billion years?

It's not clear how you'd do that with current technology.

What is the oldest unmaintained working man-made mechanism? I have no idea, but I'd hazard that it's closer to 100 years old than 1000. Things that do keep working do so because they're regularly maintained by people. I'm thinking of stuff like multi hundred year old mechanical clocks.

Assuming you mean some kind of electronics made with transistors, you would have to deal with unsolved problems including

* how you build a billion-year power source

* how you deal with transistor aging on the billion year timescale

* how you deal with medium & large scale events over a billion years (example: weather if on a planet, micrometeorite impacts if in space)

Heck even the clock of the long now <https://en.wikipedia.org/wiki/Clock_of_the_Long_Now>, a clock that works on a scale of 10k years, is a major engineering challenge that will most likely be unsuccessful (my opinion)

So, how would you evaluate whether or not you have done it? When you want to say something will last 10 years, you can utilize various techniques (running at higher temp, etc.) to simulate 10 years in, say, 6 months. But, crucially, we know that this is a reasonably good simulation, because we can compare things put through the "accelerated aging" with things that were made the same, but are actually 10 years old. So we know that they simulated aging works, at least to a degree. We don't have a reasonable way of testing whether or not something would last even 1 million years, if you're talking about electronics or anything similar, much less 1 billion, so any answer of "yes" or "no" is just opinion, loosely tethered at best to any facts.

Given a long but finite time horizon, I believe humanity could (and I believe will as well) create an AI capable of lasting a billion years. If we look at the lifespan of life on Earth, around 4 billion years give take, it’s clear that long-term systems can persist under the right conditions. If we have approximately 7 billion years left before the sun becomes a problem, creating an AI using self-replicating systems, possibly through wetware or bio-engineered components, could allow it to endure for such an extended period. The key would be ensuring that it can maintain itself, adapt, and evolve over time.

Technologically feasible? Probably and likely

No. It is not technologically feasible for humanity to produce any technological artifact more complex than solid geology that will verifiably last a billion years, and even the solid geology likely won’t last anywhere near that long.