You should impose a 15 turn maximum for each game, to prevent players from farming points to much.
There should be national objectives which nets players points. However, anyone can get them, which makes for a king of the hill style game.
E.G:
+1 point to whichever player controls Berlin at the end of the game (If its contested, nobody gets it)
+0.1 points for every IPC you collected during the final phase of the game
+1 point whenever you conquer an enemy capital (one time only, for each player)
-1 point when you suffer from economical/political collapse (one time only, for each player)
Etc.