One important thing to keep in mind is that the upper third average bench press measured was 83.8kg (~185lbs). That is still a light bench press by the standards of those in the fitness and bodybuilding industries. I would imagine that there is a limit to the longevity gains that could be made from muscle strength and that these gains might start to reverse for bodybuilders and other strength athletes due to the increased strain it is putting on your heart and other organs.