hey, I did some games in nightmare eternity, one of them was until transcendent era, maybe you could find some info how to avoid too much expenses https://forums.civfanatics.com/threads/snofru-space-map-v9-large-nightmare-eternity.674676/
about speeding up production, it causes inflation which can be a huge problem because it increases all costs multiplicatively, I try to avoid it altogether (which means keeping it at 0-1% or at most like 5%, tracking what is current value every time before speeding up, and only using it for major wonders, so that rate of turns saved to inflation is the best), now that it's too late I would consider changing all the civics to ones that reduce maintenance from number of cities and overseas kolonies (largest source), and also look at value "civic upkeep", build things that are reducing maintenance directly like (if I remember correctly) palace of soviets or giant firewall? keep crime and disease low, also some civics have direct negative modifiers to inflation (was it gold standard or planned/regulated economy?) while some others have positive (guilds or mercantile, not sure)
soon I might start another game, hopefully svn still works, so you can maybe ask me. Turn times can become problematic in later game, my pc can handle it well until around cosmic, at this point it becomes few minutes per turn
still so much better than it was some years ago, I remember these large turn times already happening on medieval era, maybe that's why there was someone calling the mod "caveman2castles"
