> I could have 20 holding pens in the house and they'd still lose their stuff, since the idea that you have to exert even a minor amount of effort <now> by putting stuff in its place to save yourself much more searching effort <later>, is either lost on them, or they just greatly value the present over the future.
That doesn't give enough credit to the original idea. I know it's an exaggeration, but 20 holding pens will totally defeat the purpose. The idea is to have one place in every room where you can put anything. This saves the mental effort of trying to recall what is the place for thing-at-point. There is a place, for all of them, don't think about it. Just dwim it into the holding pen.
That doesn't give enough credit to the original idea. I know it's an exaggeration, but 20 holding pens will totally defeat the purpose. The idea is to have one place in every room where you can put anything. This saves the mental effort of trying to recall what is the place for thing-at-point. There is a place, for all of them, don't think about it. Just dwim it into the holding pen.