Earlier quoted context omitted.
There was another thread today with the headline "If Earth Is Average, We Should Find Extraterrestrial Life Within 60 Light-Years" [0], and the grabby aliens model apparently estimates 1 billion light-years. So it seems the volume of a sphere of radius 120 million light years is at least within an order of magnitude of the space within which some models predict the emergence of life. [0] https://news.ycombinator.com/…
The big point is that any intelligent extraterrestrial life should be highly visible, and spread itself out at some fraction of the speed of light. Earth as it is right now is in a fleeting transition period on cosmic timescales. It seems unreasonable to assume other extraterrestrial life that evolves to be intelligent/space faring would stay in that state for millions of years. The universe is 13.8 billion years old…
1. We couldn't have gotten to where we are without fossil fuels and a bounty of oxygen in the air (but not so much to be dangerous). So the conditions and time scales may not be so simple or average.
2. You're pesuming hyper-intelligent races even have the desire to spread themselves like a plague into the universe. Resources are distinctly finite, why waste unfathomable amounts of energy and labor "exploring" pointlessly when, instead, most of the population can just digitize themselves and live in an eternal, simulated heaven as they sip on resources slowly and only expand when absolutely necessary. This also minimizes the risk of encountering aggressive neighbors.