When does the campaign end?

The campaign will last certain number of global turns and then the outcome will be decided using the campaign victory points.
I have not yet decided how many turns. Considering that one turn is roughly a week real time, and the speed boosting bonuses I have provided(fuel stations, starpots)it is very unlikely that it will be more than 8 turns.
That's just for information.

so what's the 15k worth of points we get? is that just in case the war drags on longer than we expected?

No, the 15k are because of point boosters like the starports which draw from them, and because I expected that at least one force will have more than 1 player as we see now.