I tell folks pack it so you can comfortably drop the package on a corner from ten feet up. And no problem.
As mentioned it is the cushioning inside the box that matters. The more weight, the denser and thicker the foam needed.
But IMO the drop from ten feet is to be EXPECTED.
My favorite horror story UPS style: I was at the main depot terminal UPS off Bluemound Rd near the Milwaukee County border with Waukesha County(not some store) and as I waited in line, A UPS employee pushed open a swinging door with a skid on wheels, carrying a very large box. The box was WIDER than the door.. However the employee refused to accept it would not fit. And began to pull back, and try to bang the box HARD ... into submission, over and over, As I and half a dozen customers watched. finally after about ten tries to force the box through the too small opening. The owner of the item walked in and started yelling. (by then my need to stay was no more,and I left. Not knowing what finally happened. I do think if the box had been rotated 90 degrees... it would have fit through the door. UPS....ups..

