I still think the argument holds in this case, because even computer software isn’t atom-less. It needs to be stored, or run, or something somewhere.
I don’t doubt that you could drastically reduce the number of atoms required for many products today. For example, you could in future get a chip in your brain that makes typing without a keyboard possible. That chip is smaller than a keyboard, so represents lots of atoms saved. You could go further, and have that chip be an entire futuristic computer suite, by reading and writing your brain inputs and outputs directly it could replace the keyboard, mouse, monitors, speakers, and entire desktop, plus some extra stuff, like also acting as a VR Headset, or video game console, or whatever. Lets say you manage to squeeze all that into a single atom. Cool. That’s not enough. For this growth to go on for those ~8000 years, you’d need to have that single-atom brain chip be as valuable as everything on Earth today. Along with every other atom in the galaxy.
I think at some point, unless the hottest thing in the economy becomes editing humans to value specific atoms arbitrary amounts (which sounds bad, even if it would work), you can’t get infinite value out of things. I’m not even sure human minds have the capability of valuing things infinitely. I think even with today’s economy, you’d start to hit some asymptotes (i.e. if one person had everything in the world, I’m not sure what they’d do with it all. I’m also not sure they’d actually value it any more than if they just had 90% of everything, except maybe the value on saying “I have it all”, which wouldn’t be represented in our future economy)
And still, the path to value per atom has to come from somewhere, and in general it’s going to be making stuff more useful, or smaller, but there’s only so useful a single atom can be, and there’s only so small a useful thing can be. (I imagine some math on the number of ways you could arrange a set of particles, multiplied by the number of ways a particular arrangement could be used, as an estimate. But a quick guess says that neither of those values are infinite, and, I expect that number to be dominated by ways of arranging particles, not by number of uses, considering that even software on a computer is actually different arrangements of the electrons.)
So I guess that’s the heart of it to me, there’s certainly a lot more value we can squeeze out of things, but if there’s not literally infinite, it will run out at some point, and that ~8000 year estimate is looking pretty close to whatever the limit is, if it’s not already over it.
Please see my other reply here. Yes, value is finite, but the number of possible states of the universe is enormously large, and we won’t explore it in 8000 years. The order of magnitude is much bigger.
(Incidentally, our galaxy is ~ 100,000 light years across; so even expanding to cover it would take much longer than 8000 years, and that would be creating value the old-fashioned way by adding atoms, but it wouldn’t support continued exponential growth. So “8000 years” and calculations based off the size of the galaxy shouldn’t be mixed together. But the order-of-magnitude argument should work about as well for the matter within 8000 light-years of Earth.)
In much the same way, estimates of value and calculations based on the number of permutations of atoms shouldn’t be mixed together. There being a googleplex possible states in no way implies that any of them have a value over 3 (or any other number). It does not, by itself, imply that any particular state is better than any other. Let alone that any particular state should have value proportional to the total number of states possible.
Restricting yourself to atoms within 8000 light years, instead of the galaxy, just compounds the problem as well, but you noted that yourself. The size of the galaxy wasn’t actually a relevant number, just a (maybe) useful comparison. It’s like when people say that chess has more possible board states than there are atoms in the observable universe times the number of seconds since the Big Bang. It’s not that there’s any specifically useful interaction between atoms and seconds and chess, it’s just to recognize the scale of the problem.