Somewhere I remember reading that screwmounts are much more tolerant of wear, since the final position of the lens relative to the film plane is determined by the seating of the lens as it is tightened. Wear on the face of the lens mount is unlikely. With a bayonet mount there is the chance that the segments of the mount, for lack of a better word, will over a long time, wear and thus the lens will not be tightly registered to the face of the lens mount. I've yet to read any posts anywhere commenting on either bayonet or screwmount wear. I suspect that the concern is mainly theoretical. Certainly you don't want to overtighten anything on any camera!
Anyone else have thoughts on this?