Washing machine supply/drain box

What is the ideal height for the supply/drain box? My washer is 43 inches to the top of the control panel. Should the bottom of the box be at 44 inches? The plumber says 48 inches to bottom of control box...

Why argue with the pro? It might not really have to be that high, but as long as the hose reaches there is no reason not to set the bottom at 48". You do want it above the top of the washer, so unless there is a compelling reason not to go to 48", I would have the plumber put it there. There should be something in the installation instructions that came with the washer to give you some direction.