Hey, I couldn't tell you, simply because I've never really finished a game.
The only one I finished was on high tech, a small grid galaxy. There were two empires, mine and the AI, and we were cut off because of no WPs between the two 'sides' of the galaxy.
That Lasted about 140 turns.
That just points out 'what do you mean by 'average' game turn'?
I personally like to trade with the AI until expansion forces me to do troop landings on all their planets. . . which is always a nice bonus.
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