Irving, Tex. ? Bill Parcells will hit retirement age Tuesday. If he takes any time to celebrate, it’ll come after he figures out what his team did wrong in tonight’s preseason game.

A few years ago, even Parcells would have laughed at the idea he’d be studying game film on his 65th birthday. Having already walked away from coaching twice and passing on other jobs, he seemed content to get on with his life and savor his legacy as a two-time Super Bowl champion.

Then the Big Tuna came back for one last shot at glory with the Dallas Cowboys.

The countdown to his next retirement started ticking the day he agreed to work for Jerry Jones. Hardly anyone expected him to fulfill his four-year deal. Even those who did figured that would be it.

Yet Parcells has made it to Year 4. And he’s signed an extension through 2007.

“He’s not entirely mentally healthy, which makes him want to keep doing this and beating himself up,” joked quarterback Drew Bledsoe, clearly savoring the chance to jab back at the coach who is going into a sixth year of jabbing him. “But I am happy for him. He can go to the movies cheaper and get senior citizen rates at the restaurants. It will be good for him.”

Parcells could be taking advantage of those benefits. Or he could be spending more afternoons at the racetrack and nights watching pals Bob Knight and Tony LaRussa run their teams.

Instead, Parcells keeps going, energized by the realization this is likely the final chapter of his career.

Dallas Cowboys coach Bill Parcells rubs his head after a receiver dropped a ball during training camp. Parcells, whose Cowboys play the Saints tonight, will turn 65 on Tuesday.

“This is my life’s work,” Parcells said at the start of his 19th NFL training camp as a head coach, his 23rd overall in the league and 38th as some sort of football coach, dating to his first job: defensive assistant at Hastings College in 1964.

“This is something I have enjoyed, for the most part,” Parcells said. “I have been fortunate – one, to have the opportunity and, two, the longevity is not a common thing in the NFL.”

Health drove him from his first head coaching job, with the New York Giants. It was there that he carved his reputation as a defensive-minded task master. His two championships certainly helped.

After two years of talking about football on television, he returned to coach New England. He got the Patriots to the Super Bowl in an entirely different way, letting Bledsoe set all sorts of passing records.

A split with management that produced his most famous quote – “If they want you to cook the dinner, they at least ought to let you buy the groceries” – resulted in him becoming coach and chief football operating officer of the Jets. Another turnaround followed, with New York reaching the conference championship.

With the Cowboys coming off three straight 5-11 seasons, Parcells knew he could leave the club better than he found it. The money wasn’t bad either, especially for a guy coming off a costly divorce.

While Parcells has seen Bill Belichick pass him in number of Super Bowl titles, some things have worked out in Dallas, such as his relationship with Jones and Jones’ son, Stephen.

Parcells has remained loyal to all decisions made by their three-man committee, including the signing of Terrell Owens. If there’s been any friction between the big-ego bosses, insiders are doing a great job of covering it up.