I've seen the tin coating on bearings still there after tens of thousands of miles and that tin is very thin. And there are many engines that have had two or three top end overhauls and the mains and rods have not been touched, because they are not showing any wear. If changing to a thicker oil has gotton to the point of causing bearing wear, I think you'll see more than just a little wear. You would not be talking about wear, at this point, you'd be talking bearing failure. Bearings and engine manufacturing is becomming so precise that babbit, lead and copper are being replaced by aluminum bearings. Soon, a bottom end of an engine will never have to be touched for it's whole life, something that is already happening in many high quality engines, even to the cheapest rice rocket.