It's also statistically unlikely that two intelligent life planets are close enough to each other to ever make contact unless we can travel significantly faster than the speed of light.
Additionally, technological civilizations carry the seeds of their own destruction. e.g. a high-schooler doing gain of function research on Ebola in his garage. I could well see an upper limit on such civilizations at around a thousand years.
It's also statistically unlikely that two intelligent life planets are close enough to each other to ever make contact unless we can travel significantly faster than the speed of light.
Additionally, technological civilizations carry the seeds of their own destruction. e.g. a high-schooler doing gain of function research on Ebola in his garage. I could well see an upper limit on such civilizations at around a thousand years.