That reminds of the quote from General Patton when he said,"It's good that you men are brave, and willing to die for your country, but the object of war is to make the enemy soldier die for his."
Same thing, isn't it? The object is to hit the other guy and to see to it that he doesn't hit you. The object is to see if your opponent can take a punch, not to see if you can take his.
If you are asking if somebody who has ring experience can become invulnerable to punches, well:
Joe Louis got knocked out, didn't he?
Or what about MIke Tyson? OR, better yet, I love that quote from Lennox Louis when somebody asked him about the time that he was knocked out, and his response was,"If you had gotten hit with that punch, you would have been knocked out too!"
My understanding at this point is,anybody, no matter who they are or what their background or level of experience, if they get hit hard enough in the right spot, they're going down!