Do massive deals have lasting value?

The extensions always sound great the day they are signed. Owner ponies up! Player agrees to stay! Shiny, happy people all around.

Not to sound like a grump, but check back in a few years, after the player’s body starts to betray him and his team starts wondering how to minimize the damage.

These $100 million contracts are the price of doing business, no doubt. Whether they qualify as good business is another question entirely.

The spending by teams in the last two months offers a staggering snapshot of a sport that is flush in cash — and a disturbing snapshot for anyone who has studied the history of such deals.

Among pitchers, Felix Hernandez received his big contract, followed by Adam Wainwright and now Justin Verlander, with Clayton Kershaw on deck.

And on Friday, just hours after the Tigers announced their seven-year, $180 million commitment to Verlander, the Giants went to nine years, $167 million with catcher Buster Posey.

Only one catcher — Joe Mauer at eight years, $184 million — has ever received a larger deal. And if the Twins had to do it all over again … uh, let’s not go there.

Posey, 26, is this generation’s Derek Jeter, an MVP and winner of two World Series in his first three seasons. His contract is problematic because — like Mauer — he is unlikely to remain at catcher long term, and his offensive production would be less valuable at other positions. But compared with the recent pitching deals, the Giants’ $167 million bet on Posey is downright rational.

Johan Santana, anyone?

In 2008, the Mets signed Santana to a six-year, $137.5 million contract entering his age 29 season. Now Santana likely is heading for his second major shoulder surgery, one that possibly will end his career.

His totals as a Met: 717 innings, 46 wins.

Others in baseball viewed Santana as a dubious investment from the start — Yankees GM Brian Cashman told the Newark Star-Ledger’s Andy McCullough, “We had data that indicated that this was a high-risk player going forward, health-wise.”

Santana, 6 feet and 210 pounds, had a smallish frame, his fastball velocity was down, he was throwing his slider with less frequency. But the truth is, all of these pitchers are high-risk players. Some are just riskier than others.

And if any of the recent deals proves a wise investment, it will be an upset.

Verlander, 30, would appear to be a lower risk than most; in seven full seasons, he has yet to go on the disabled list. But considering his sizable innings backlog, how will he look at 36 when his new contract ends?

Again, I understand why the Tigers are committing to Verlander for seven years, even though they already had him under contract for the next two. I also understand the motivations for the Hernandez and Wainwright deals, just as I will understand the Dodgers’ logic when they lock up Kershaw.

You want to keep your ace, you pay the going rate. You generally need such a pitcher, or more than one, to win a World Series. And good luck replacing that pitcher if he departs.

That’s the conventional wisdom, at least. But the Rays, a low-revenue team that cannot afford to retain their best pitchers, demonstrate that there is another way.

The Rays can’t even afford to keep a James Shields long term, much less a David Price. Yet they continue to develop top young pitching, surviving just fine.

Hall of Fame general manager Pat Gillick had the right idea — no contracts of more than three years for a starting pitcher. The Phillies, for whom Gillick was GM through 2008, gave Roy Halladay a three-year deal, and since have gone five on Cliff Lee and six on Cole Hamels. The deal for Halladay, which began when he was 34, now looks like trouble.

Adhering to Gillick’s three-year rule no longer is realistic, particularly at a time when the annual national TV money for each team will double in 2014, increasing from about $25 million to about $52 million.

Still, why did I keep writing that the Mariners should trade King Felix? Because I felt that the return ultimately would benefit the franchise more than Felix on a $175 million deal.

I may be wrong about that, but only a handful of pitchers have provided strong value on long-term contracts: Randy Johnson, Mike Mussina, CC Sabathia (so far), maybe a few others.

Verlander could prove an exception, just as Posey could prove an exception among catchers. Thing is, you wouldn’t bet on it. And their respective teams just did.