For its part, the McCain campaign has come to the opposite conclusion.
They will be prepared to show McCain's "home" in Hanoi by using images of his cell. They claim they have not overused the POW element and insist they have "underused it."
There's no indication that McCain aides were kidding.
In case there were any doubts about McCain excessively exploiting his service, even the NYT's Maureen Dowd is calling McCain out: "McCain is now in danger of exceeding his credit limit on the equivalent of an American Express black card. His campaign is cheapening his greatest strength -- and making a mockery of his already dubious claim that he's reticent to talk about his P.O.W. experience -- by flashing the P.O.W. card to rebut any criticism, no matter how unrelated."
Given that the campaign apparently believes it's been "underusing" the story, I suppose we can expect this to get considerably worse.