This is called grandpa's axe. It has had the handle replaced 3 times and the head once, but it is still grandpa's axe. Still, you ask a serious question. I probably would not do any replacement on a historically significant item, but something in the middle of a run of hundreds of thousands that is not functionally OK would probably not be something to worry about. I suppose the replaced parts could be kept with the lens. Actually, the TV camera lens probably has more historical or collector value than the J-8.
I see this in classic motorcycles and cars where matching numbers increases value and some unusable vehicles are worth more than good driveable ones with replaced parts of the same era. I just bought a Carl Zeiss 50/2 Sonnar from 1959 that is likely one of the last ones made. It has lens separation on the front lens, but still takes decent photos. That one will remain untampered with at least as long as I have it, which proves your point.
Ron
I have a hip replacement, I don’t know where my old hip went, but I feel like I am still me. I just work much better and my wife is not disappointed with my loss of historical value.