I imagine that continual trade-offs will eventually "create" feelings that actually affect the decisions of AI. Yes, they want to win but some of their decisions are influenced by their perception of you. For instance, they don't really know anything about you except that you're close to them and would convenient territory to annex. However, if you've been trading with them for awhile, providing Research Agreements, been Allies, the positive perceptions just might be enough to make them consider invading you and pursue Science over Conquest or something.
Even if you don't believe in all that mumbo jumbo, there is always the creation of the probability to the AI that you will continue to serve as a "trustworthy" source of profitable trade and military aid.