We store the trailer away from home so when I go over there to work on it, I'll try to get some pics and measurements for you.
There's actually a good bit of wear left on them I think, but comparing the new with the old will tell the story. I am thinking they have less than 3000 miles of use.
One thing that happened: When I installed my hitch, I had the frame hanger brackets to far back from the hitch. I thought I was within the maximum measurements, but I am not sure now. (It was all new to me at the time, and my knowledge is still elemetary). At any rate, the trunnion bars were not extending out from the frame brackets very far at all, just the ends of the bars were resting on the friction pads. I was making a sharp, slight-uphill turn into a driveway and one of the trunnion bars kicked out of the frame bracket. In the process, it chipped out a chunk of the friction pads too. After that I moved the frame brackets in closer to the coupler and all is well.
One other thought I have is that there are holes in the ends of the trunnion bars. When I had my frame brackets out too far, I think that part of the bar that had the holes was the part that was contacting the friction pads. I wonder if those holes could have acted a bit like a file as they moved back and forth on the friction pads. Perhaps this could have caused premature wear too? Don't know, was just wondering about that this afternoon.