Our record is 5.5 hours for a 7 player game, 3.5 hours for a 4p game and we are convinced we can keep improving on it. But last night we spent more than 8 hours on a 6p game. I had a few ideas:
1) Don't bother including anyone who isn't actually going to be into it. If someone is going to be sitting there snoring at the pace of the game for several hours it's going to drag the whole group's energy down. People need to care enough to pay attention - if they aren't paying attention the game will take forever.
2) Attention is a limited resource. Some people like music, I personally feel that music with lyrics can be distracting if it's too loud. Minimize distractions. Coffee helps. Don't smoke pot.
3) Everyone needs to pay attention, but more than that, it helps if one or more players can actively manage the flow of the game, like "Ok, player X just went, it is now player Y's turn. You're just building in your home system? Ok, player Z, if you're just doing the same you might as well go ahead and start while player Y is still finishing." With initiative rotating the way it does in this game, sooo much time is lost in that time between turns, until finally someone says "Whose turn is it?" In an ideal world everyone would take responsibility for identifying the player who acts after them and informing them that it is now their turn, informing everyone what the secondary ability of the strategy card they just played is, etc. Too often somebody plays their strategy card (leadership, for example), and announces it, and the entire table STILL misses it somehow because so much stuff is going on in this game.
4) It really helps if people can plan their turns out ahead of time. This isn't always possible but quite often it is. Builds in particular eat up a ton of game time, if you know that your next move is just going to be a build in your home system you should really have that move ready to execute by the time it gets to your turn.
Balancing these considerations can be tough! Spending your spare time thinking about the board state and planning your next move can mean that you don't pay attention to what is going on. The more players are actively involved in managing the flow of the game and making sure everyone knows what is going on, the better it will be. If only one person is taking responsibility for this, what happens when that person also has to take some time to think about their own moves/builds/plans? Again, attention is a limited resource.
As for game rules that speed the game up,
1) The alternate strategy cards from Shattered Empire are almost a must
2) Artifacts (add more victory points)
3) A pre-set map. It takes long enough to unbox everything as it is, this should save a lot of time.
4) Don't use distant suns, or political intrigue.
I haven't played with simulated early turns but it looks pretty lame to me.