If we consider contact sports as well as high impact sports such as basketball and tennis, elite play Can continue well into the 30's. DG certainly has some high stress points on specific joints, but it doesn't compare to many other sports from a load standpoint nor a frequency standpoint.
How many max reps do football and basketball players go through on their ankle, knee, and hip joints? Add in the physical contact. Many players are done before 30, but there are a lot that continue to be the best of the best.
I would think genetics plays a part. Maybe a huge part. Maybe PMB doesn't have Tom Brady like genetics and no amount of training or ice baths alters the equation. I don't know.
But, if it is a work ethic and skill question, I feel certain Paul will be back in the hunt in the years to come.