Big Joe's age is far less of a concern for me than his slow-fast speed equilibrium is. Weight and age can affect that but having someone in his camp who actually understands the concept of slow-fast speed and how to achieve the correct balance, ideally a slow-fast speed fighter or someone who has extensive experience training slow-fast speed fighters, especially elite ones, is far more important.
The big problem with Joe is that he hasn't been training as hard as he used to. He's been coming in extremely heavy since the first Zhang fight, which has resulted in him being even slower than usual. If he gets his weight down he can be in some decent fights, although his days as a genuine contender are most likely over.
Usually I agree with the concept of a tune up after a loss to boost confidence but after some reflection I'd say no..He's lost 3 of his last 4 fights and has looked absolutely dreadful in them. Add to this that he turns 40 this year and his options forward are seriously narrowed. I think he should grab the cash a Wilder fight would bring, plus Wilder is 39 and has looked awful in his recent fights. If Joyce could rush Wilder early and land on his fragile chin he could snare a win. But with two old fighters who have one foot out the door any result could happen.