Interesting. What happens when you turn this off?Correct, this is exactly one of the considerations that goes into AI war declaration frequency.
The reason I (and most players, probably) pretty much never play more than 200 years into a given game is that no AI, no matter how big they start, can match my blobbing speed, which means I inevitably become way bigger than everyone else and there's no point in going on anymore. I didn't know it was intentional.
A more aggressive AI could make lategame more interesting.