Hi,
I just noticed something I should have noticed a long time ago regarding Court Sessions; you're taking Free to mean there is no GB cost. That's not correct. Each Free diplomacy action that you participate in costs 1GB (representing the considerable effort put in by the domain). It's only 'free' in that it is a Free Action.
If it worked any other way then it would be advantageous to make a few big court sessions once in a while and go amok with 0-cost diplomacy. That's not how it's supposed to work.
So from turn 66 - remember to pay your 1Gb for participating in diplomacy.