Worth it to balance rotating assembly?

Always have them balanced, every time rotating assembly parts are changed. When the rear view mirror walks around on its ball at 50 mph, and your vision gets fuzzy as the dash screws turn in and out by themselves at 60 mph, and the rear main seal leaks after only 20 miles you will kick yourself for being stingy. As at that point you face a complete tear down and reassembly which is lots of time, gaskets, and two more round trips to the machine shop. Just do it right the first time and sleep well.