The best way to prevent milking the game is to design a scoring system where the perfect score is zero and you can only lose points.
Something to think about
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A strictly negative scoring system can always be translated into a positive one if you want to be wussy - it's really a system which HAS a perfect score. As an example of this imagine a game where you have to win by cultural victory. A milkable game is one where the total culture of your empire is used as the criteria - an unmilkable game is one where it's the culture in your poorest culture city (maximum culture of legendary - overflow not counted), minus 5000 points for every time you lost a city. In this case the perfect score is having legendary culture in your poorest city - in other words a 3-city Cultural Victory.
A perfect score system has the downside of the possibility of several people getting a perfect score - it's hard to declare a winner. But this isn't a problem if the goal is variantland and not competition, also perfect scores can be unattainable making a winner more likely. Of course a perfect score system isn't automatically good - if you're penalized for every land tile you don't control then that forces milking the game to acquire as much land as possible...
Something to think about
.A strictly negative scoring system can always be translated into a positive one if you want to be wussy - it's really a system which HAS a perfect score. As an example of this imagine a game where you have to win by cultural victory. A milkable game is one where the total culture of your empire is used as the criteria - an unmilkable game is one where it's the culture in your poorest culture city (maximum culture of legendary - overflow not counted), minus 5000 points for every time you lost a city. In this case the perfect score is having legendary culture in your poorest city - in other words a 3-city Cultural Victory.
A perfect score system has the downside of the possibility of several people getting a perfect score - it's hard to declare a winner. But this isn't a problem if the goal is variantland and not competition, also perfect scores can be unattainable making a winner more likely. Of course a perfect score system isn't automatically good - if you're penalized for every land tile you don't control then that forces milking the game to acquire as much land as possible...
