I was about to make a grey goo analogy, but then I read your second paragraph :) Those are my thoughts as well: for the purpose of the Fermi Paradox, it doesn'

I was about to make a grey goo analogy, but then I read your second paragraph :) Those are my thoughts as well: for the purpose of the Fermi Paradox, it doesn't really matter whether it's machines or not - it doesn't even matter if they're "conscious", they could be the equivalent of bacteria colonizing everything. I think you nailed it on the head when you said their drift rate largely determines their future. I consider beings with (for lack of a better term) high general intelligence to be innately high drift organisms, whether their actual replication processes are locked down or not. The drift they experience will be guided by volition. Whereas machine bacteria (which we are) would be subject to traditional evolutionary processes. I'm really uncertain about the prospects of locking down the latter with high error correction, because it takes only one such bacterium with a random mutation to escape the error correction mechanism and voilá we're off to the races. It's worth noting that organisms on Earth have a high variability when it comes to their mutation rate, which suggests the mutation rate itself is a parameter guided by a fitness function rather than an inherent byproduct of our specific biological substrate. Of course I agree with your intuition that much higher error correction rates can probably be achieved in architectures other than DNA/RNA. In the end this is mostly a meditation on how static life in the universe will end up being. Not just regarding the time frames but also the depth of change. On balance, I suspect we'll end up with a highly variable ecosystem just by virtue of more pathways leading to that future.