Around the summer of 1973, I worked as a helper for a small pipeline contractor in Iowa and they dug the trench with a Unit Mfg.excavator. Indeed that operator was a busy fella yanking those levers. I remember he'd take the outer break shoes often to be re-lined down to some shop in Des Moines every now and then. At the mine I worked at we used what's called slushers which is basically a drag line without a mast to muck out the draw points. They re-lined the shoes on those in a shop onsite....I think of the awesome skill required to know which cable drum operated which part of the assembly. Much more skill than operating a modern backhoe, or shovel. Also, I imagine they operated a lot slower than hydraulic excavators.
Jim