I know Yeerk security isn't as good as it could be, but I really don't think they'd let some voluntary stroll around anywhere near the exit, even if Aftran said her involuntary host had just recently decided she was ok with being a controller. Right in the first book Jake and Marco were spotted not doing anything and someone demanded who they were. Everyone is being watched. If you aren't exactly where you're supposed to be, you're busted. I don't care how voluntary someone is, the Yeerks are serious about what they do.
I said before this is a plot hole. Fill it in however you want, just try not to Voodoo Shark it, if you know what I mean.