Joint locks are another matter since you can get an injury that seriously affects your career. Big Nog probably should have tapped earlier but I understand why he didn't. If he were a younger guy with his whole career ahead of him then I would be more inclined to criticize, but if one of the real legends in the sport wants to go out on his shield then I think that's his prerogative.
He tapped AFTER he got his arm broken in 2. That sucks.