Dune game length

So I recently bought and subsequently pimped out a copy of Dune. We've played it three times so far, we're loving the game, and are obviously still learning a lot about the game, but damn, is it taking loooong. By long I mean that the latest game had finished turn 6 (in a game where getting to 15 turns is a win condition for one faction) after 4 hours, when someone had to leave. Roughly, this means that if the Guild were to have gone for its special win condition, the game would have taken 10 hours (game 2 took 7 hours, and went until something like round 7).

In a thread a while ago on Dune, Michael Barnes mentioned that one of the drawbacks of Dune is that it has variable play length: "anywhere from 30 minutes to 5.5 hours". I would be THRILLED if 5.5 hours were the upper limit; heck, I'm shooting for 6 hours as the upper limit, with 3-4 hours as average; is this unrealistic?

What do people do differently than us that is making us so slow? How long does the average round take for you guys? How long does it typically take for each player to make their shipment/movement? Are we attacking or defending too much, causing too many long combats? It doesn't feel like we're speeding up a whole bunch after getting familiarity with the flow of the game (we're just playing with basic rules, no optionals).

DUNE has a real volatility in its duration that is probably its only real design flaw, and even then it's not a flaw so much as an inconvenience.

I don't have metrics on turn length, combat time, etc. but I find that playing with people who know the game pretty well (as usual) makes a big difference. If everybody knows the powers and the interactions- and is able to identify certain situations and circumstances ahead of time- the game goes a lot quicker.

I think most games are going to be in the 2-4 hour range. Your games, I'm not sure why they went so long. I've never played longer than 5 1/2 hours, and that was a game that was filled with a lot of goofing off and we didn't get a nexus until like halfway through the game.

One of the things that makes Dune so great is that games can twist and turn so much. But that does mean games can take a long time. One of the things that makes games take a long time is people going into battle when it is not worth their while. Big fights always set you back so they are only worth it for big prizes.

Six and ten hours do sound extremely long. You say shipping/movement is taking a long time. You are playing that you can only make one transport per turn and one across planet movement per turn.

Yeah, we're definitely playing the rules right, it's just that people are taking a long time to make their transport and move, largely due to allies talking it over, enemies bribing them to go elsewhere, (i.e. all the fun stuff!) and the fact that it seems like it's highly dependent on what the previous people do, so you can't really have it all planned out while other people are moving.
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People going into battle when it is not worth their while I can DEFINITELY tell is dragging us down. That was my first guess as to the problem: I'm seeing the problem I sometimes see with Cosmic Encounter newbies where they think that, if someone is attacking or being attacked for the win, there is no reason not to go all out (whereas, as the offense, you should wait to go all out in a battle you can actually win, and as the defense, stopping someone else from winning is not the same as winning yourself, so you should hold back your real best stuff for when you're going for the win yourself). This is leading to a bunch of battles where everyone dials almost all their guys, leaving barely anyone anywhere so it always seems a good idea to attack all the time.

I'll try to point that out to the group next time: not to go into battle unless it's really worth it. That same kind of thing dragged out our first Twilight Imperium game a while ago (I've got a war-hungry group!).

Do most games end in the first 7-8 turns or so, or is that only happening because everyone is constantly trying to win (partly because we're tired after so many hours)?