I am usually a diplomatic player and I try to avoid the long wars, In a recent gigantic map game I stumbled on a strategy that seems to work well at the challenging level.
I colonized all the high PQ planets in my part of the galaxy with the intent to come back and pick up the 6-7 PQ later. I was well established with influence and diplomatic tech when the AI came in with their slow, long range colony ships and started picking off the low PQ planets in my influence area.
Within 3-4 tuirns all their colonies had the skull and cross bones and with in 20-30 turns they started flipping. As the planets flipped my influence area started to spead and it was a domino effect. By the 8th year I had a cultural victory.
I only had one war, with the Altarians because I was evil and because I got the assassination event. I beat them bad until they sued for peace and they remained cool but under control throughout the game.
At the end the planets were flipping so fast I didn't have time to manage the planets and apparently none of the AI had time to surrender to another AI.
By allowing them to come into my influence zone their borders were too close to me to resist my influence.
