Improving print speed by adding holes
Holes in vertical walls will make it take significantly more time to print, not less. Rather than being able to make a continuous path around the box on each layer, keeping the print head at the desired speed the whole time, the printer will have to run around each connected component of the layer separately, slowing down, retracting, speeding up to travel, slowing down at the destination, unretracting, and speeding back up each time.