I never seem to have an outlet where I need it, so my first response to your question was "Put the plugs every where you can!" Or at least put one every 4 feet or so. You are so smart to put them halfway up the wall!
I have a 1930's dresser that has an outlet on one of the dresser legs. While I have never used that particular outlet, I can understand why it is there. Back then, outlets were few and far between in a room, and the outlet on the dresser let you put an extension cord from the wall outlet over to the dresser.