It's both, I think. His build and the fact that he plays so hard when he's in there are big factors in him getting so worn down, but age is what keeps him from being able to bounce back.
We relied on him so heavily in the Dallas series that he didn't have anything left in the tank for Portland. All of the close monitoring of minutes for an entire season was pretty much shot in those seven games.
I'd like to think that a couple of extra days off can refill his tank, but age is a tough wench. You just can't bounce back like you used to be able to. We shall see.
[This message has been edited by DTP02 (edited 5/13/2014 1:47p).]