Done some thoughts/math on the maximum number of campaign turns in CC
As each campaign turn generates atleast 2 or 3 Campaign victory points that can be won by either side, then you will have with:
4 players maximum 9 campaign turns. (to reach the 9 points that ends the campaign)
6 players maximum 8 campaign turns. (to reach the 12 points that ends the campaign)
And this only happens if the Campaign victory points is equally distriputed between the two sides and if there are no victory bonus points scored from battles played at bases.
On the other hand, if one side totally Blitzes the other side in the CC campaign by winning and scoring maximum Campaign victory points in each campaign turn.
Then it could all be over by the second campaign turn. As you can score up to 6 or 9 Campaign victory points per turn.