In my current game I have two factions that have 28 thousand or so total research value. I have researched everything myself with a total of 16,254 spent and 10,400 research remaining. My research path may be slightly more efficient than what the AI takes but I suspect the AI is sitting on heaps of extra research it can't use because it's probably maxed out on the technology tree.

I suggest making it so if the AI factions have no more technology to research they stop building new research stations and either turn off their existing research stations and stop accepting new goods into them or they should scrap their research stations at that point of the game. Presumably they would still gain research points occasionally through capturing enemy stations or ships.