What's to keep any controller from pulling the plug out? Although morphing something that doesn't have outer ears, or has ear flaps like Crocs, could be useful.
I don't know if there's evidence or anything, but going in through a certain ear repeatedly might make it easier to go through each time. I figure some Yeerks might have a certain preference. The first time could be a random ear, and subsequent infestation could usually be the same ear. But when the other controllers working at the pier are forcing a head down, they probably don't keep up with which ear is the designated ear. They are probably more concerned with efficiency. Just get the head down, pull the host up, and move on to the next step.