Well, there are plusses and minuses. At a certain level of size, connectedness, and semi-specialization, you get (what we label) consciousness. It's not just

Well, there are plusses and minuses. At a certain level of size, connectedness, and semi-specialization, you get (what we label) consciousness. It's not just size, but there is some bare minimum of nodes. It's not just pure contentedness. That's just noise. It's not just specialization. It helps with speed, but you lose plasticity and adaptability. Also, there's a physical limit with respect to growth speed 'cuz cancer and sustainable metabolic rates wrt food intake, digestive efficiency, and thermoregulation. It seems the shrews and moles have "hacked" that in very different ways. There's also a physical limit with brain size for live births--which we're already really, really pushing. Honestly, I would've thought the most intelligent species would use eggs to minimize the trauma/risk of live-births to both child and mother, but I guess mother's milk is so beneficial it makes up for all of that.