[Wanderer]

I can agree with some of what your saying. When I play, I tend to stripmine a planet down to 0/0/0 and turn it into a research/intel facility after that. If I want to keep mining that planet, I can build a value improvement plant. Perhaps, the AI should build more of those.

Unless I am very much mistaken, the AI can upgrade facilities, but not replace them. Those planets it fills with mineral miners in the early game will remain like that...

Between human players it depends a lot on maintenance reduction bonuses and careful planning.

Space vessels are not run on abundant charcoal and saltpeter. I imagine they run on things like uranium

Current space ships (e.g. the Space Shuttle) use hyrdogen fuel cells (hydrogen + oxygen & a catalyst = electricity + water?) and solid oxygen fuel. Hopefully in the future they'll have nuclear fusion working - as fusion only requires hydrogen, which is rather abundant in the universe.

A technologicallly advanced race (e.g. Asimov's First Foundation) would be able to work out how to use dwindling resources efficiently.