<GameTurnInfos>
<GameTurnInfo>
<iYearIncrement>1</iYearIncrement>
<iTurnsPerIncrement>108</iTurnsPerIncrement>
</GameTurnInfo>
<GameTurnInfo>
<iSeasonIncrement>2</iSeasonIncrement>
<iTurnsPerIncrement>500</iTurnsPerIncrement>
</GameTurnInfo>
</GameTurnInfos>
I'm not sure what you'd DO with 608 turns, mind you. Just that you'd have them.
Make sure you're playing on an appropriate speed level - like Epic, i'd guess. Looks like it's 300, 600, 900 ... so 608 is Epic.
I suspect the 300 turn issue is largely relegated by the advantages of Epic - even if it takes longer to do things, you feel better about it. But that's a personal choice of course.
I do suspect that 600 turns on Normal is absurdly long... but then again you don't have to take 600 turns to finish the game, either.