I got to thinking about this a while ago: Would the Yeerks have stopped invading other planets once they had taken over Earth?
The reason why I'm thinking this is because of the insane amount of humans we have on this planet. If the Yeerks had taken over, wouldn't they easily be able to find a host for every Yeerk in the Pool Ship? I think there were millions of Yeerks at most, where as we have billions of humans on this planet (all who could reproduce really fast too, if needed).
To me, the whole point of the invasion and the war in the first place was that the Yeerks wanted to be free, and to see the world as other creatures did, which is why they escaped from the Andalites after they were given portable Kandrona Rays. The Yeerks then went going around the universe looking for a Class Five (?) species where they could permanently settle their species into. From what I remember of Visser, humans were that set of species that they were looking for.
Am I not right? Was that not the objective? Do you think that if the Yeerks had taken over the humans, that the objective would've been completed? Would they have been content with living their lives as humans? Or would they lust for more power, invading as many planets and species as they could find?