I like the bolt in for areas with high load or vibration. I worked in manufacturing plants for about 16 years, most of the equipment was either Westinghouse or Square D bolt in type, all of it gave vary little trouble. As far as maint. goes we would shut down the panels once every other year and check the screws for tightness, I do not remember ever tightning one more than about 1/16 of a turn, of course all this was wired with copper wire, as it should be in an industrial setting.
