... a few years in realtime ...
In the Transcend, they can "clock up" to a very high level. Living a million seconds to each one that passes in realtime.
What would it take to create / adapt an intelligence that would last that long without falling into a very deep rut, as far as thinking goes? Maybe they've died of boredom, maybe they've discovered everything they originally sought to learn, maybe they've Sublimed (yes, I know, that's a Culture series thing) or otherwise gone to a higher plane of existence.
It would have been interesting to explore this further, but perhaps Vinge didn't think he could pull that off.
Always tantalized by that idea, but always wondered why that would necessarily be the case ...
This is indeed in A Deepness in the Sky. You're the first person in this discussion who's brought this up. This, to me, is the most important insight of Vinge in the Fire/Deepness series.
>Always tantalized by that idea, but always wondered why that would necessarily be the case ...
It's pretty obvious; those with the power to deploy such surveillance are always tempted to use and abuse such power. (EDIT: Let me reword this. Those with the power to deploy such surveillance methods inevitably deploy them. Smart dust is far, far, far more all-encompassing and inescapable than having security cameras on every street corner. The combination of these two things inevitably destroys civilization.)
Because the traders in A Deepness in the Sky use coldsleep and visit planets every few decades or centuries, they notice big changes that occurred incrementally.
No, he was not because his ideas about "the nature of the cosmic dark forest" - allthough having at least some internal consistency - lack any foundation in actual science and his ideas about "higher dimensional space" were pure nonsense.
They were not "answers" but plot devices.
It doesn't mean providing a hard scientific explanation for something that supposed to be beyond our scientific knowledge. Who took out the protomolecule builders and why? Leviathan Falls will likely provide some answers. Same with Death's End giving more details about the Dark Forest. It's an exploration of an idea, not a documentary.
Imagine criticizing Dune because the spice and sand worms aren't based on actual biology.
That's the root cause of our disagreement. I simply call that a good story. On the other hand, to me a book gives "interesting answers" to something if it has something meaningful to say about reality, not just the fictional universe.
In Dune, that would be true for politics and religion but not for sandworm biology.
But that's guaranteed to be the case when it comes to aliens, since we don't yet know of any. Even if someone uses a more plausible resolution to the Fermi Paradox in their story, it will still be based on speculation, instead of telling us something about reality, since we simply don't know.
So in the context of ascension and aliens, it's all fictional and down to whether the writer can deliver a creative enough explanation. To use a fantasy example, that didn't work out so well for the Game of Thrones tv show, and might be a reason why GRR Martin is taking so long to finish the books.
In case of the fermi paradoxon, I'd add the first two books of Baxter's Manifold series where he offers two distinct explanations, the first one being "it's not a paradox at all, we're truly the first" and "some natural process is killing them off before they can colonize the galaxy".
Now, we don't know if they're right because, as you pointed out, we never met actual aliens. But that doesn't change the fact that their assumptions is based on actual science.
Klingon mating rituals, on the other hand, are not.