From my AAR (.913 large map, ridiculous AI, dense everything)
Turn 11: Level 3
Turn 21: Levels 5,1
Turn 31: Levels 5,3
Turn 41: Levels 6,4
Turn 50: Levels 7,5,4
Turn 60: Levels 8,5,4
Turn 70: Levels 8,7,5,6
Turn 80: Levels 8,8,5.6
Turn 90: Levels 9,9,7,6,6
Turn 100: Level 10,11,8,6,6,7
At this point, the game was won (as in, no challengers really left) and I stopped
From my single city/single hero/quest victory (.914, all setting maxed as above)
Turn 12: level 5
Turn 74: Level 14
Turn 158: Level 27
Turn 202: level 35
Turn 235: Level 38 - victory