Age doesn't matter in his case, but the years active as a pro. It's his 11th year now. We had a thread here were someone calculated the stats and on average most fighters decline significantly after 9 years of pro MMA. And in particular the Chute Boxe style of fighting isn't really health keeping.
That's exactly it. Age isn't necessarily the most important factor here, it's the mileage. The exact same thing happened to Wanderlei- ironically, from that same Chute Box camp. Now there's always an exception to the rule, but when you take Shogun's injury history into account, I'd say the odds are stacked against him at this point.
As has been the case with B.J., you have to question Shogun's motivation and dedication to training at this point. Unlike B.J. however, it's encouraging that Shogun is willing to change things up in terms of his training, and surround himself by different people. I'm rooting for him, because the dude is tough as they come, but he represents that old guard in MMA that seems to be getting passed by. I mean, when you really think about, the only time he's looked in top form (or close to it) in the UFC has been his fights with Machida.