I don't know if the original poster is still paying attention to the thread since it's been a month, but I thought I'd pass along the answer I found. I too prefer slow, build-up type games which last far longer than normal expectations. So, I poked around in the XML files and found a way to extend the game's life.
The file is:
\Assets\XML\GameInfo\CIV4GameSpeedInfo.xml
Make a copy of the file just in case. Rather than creating a mod, I modified the base files to keep things simpler. Open the XML file in Wordpad or something. The section you're looking for is:
<Type>GAMESPEED_NORMAL</Type>
Then scroll down to find:
<GameTurnInfos>
<GameTurnInfo>
<iMonthIncrement>12</iMonthIncrement>
<iTurnsPerIncrement>300</iTurnsPerIncrement>
</GameTurnInfo>
</GameTurnInfos>
</GameSpeedInfo>
If you change the iMonthIncrement to 1, the game advances 1 month at a time on the clock. This does not effect your total game time available before the king ends things however.
If you change the iTurnsPerIncrement to say 12000000, you will get 12 million turns. (I actually did this as an experiment and the game didn't balk. It shows that many turns until revolution.) Set this to however long a game you want to be able to play.
Use a really large number if you don't want any pressure to revolt against the king. But if you do this, be aware that the market prices tend to lower over time. I had one game where silver dropped to half it's original prices. I haven't figure out the fix for this too.
If you want to have the date make more sense, you can also go into the GlobalDefines.xml file and change the START_YEAR. In my testing, I set it to 1.
