He's coming to the end of his career. The body can only tolerate drug abuse for so long before a major organ fails.... 10-12 years tops.
Dex has been competing for far longer that that, well over 20 years (15 as a pro, and a successful one at at that).
He states he's feeling better than he has in years. And, as long as he's winning and placing high, there's no need for him to stop.
His only complaint, in my view, should be Masters Olympia. Maybe they should go back to calling it the Masters Pro World Championships. Dex got $100,000 for that win in 2011. He only got $75,000 for the Masters Olympia last year. I thought the moniker "Olympia" added more prestige (i.e. MONEY) to the title.