If you live long enough, you'll see everything, including things you never expected to see.

Such as local celebrity (alleged) mob boss Joseph "Skinny Joey" Merlino pleading guilty to a charge, something he never did before. As recently as 2016, when Merlino was one of 46 men charged with racketeering, 45 pleaded guilty to reduced charges. Not him.

That stubborn streak ended last week. He went for a relatively minor gambling beef, but still it was a first, a tectonic shift.

It will mean more jail time for a guy who has spent about one-third of his adult life behind bars at Club Fed. Maybe at 56 he's lost some of the gangster edge and is looking ahead to spending his remaining days quietly with family and friends.

News of the plea deal stunned defense lawyer Chuck Peruto, who once represented Merlino.

"I'm shocked because he would never even entertain pleading guilty on any case, he always fought," says Peruto, who defended Merlino after he (allegedly) spit in the face of a Longport cop at the Jersey Shore and then tore up a court summons.

"I got him a beautiful deal of what amounted to a summary offense," Peruto told me. "He said, 'No, I don't plead guilty.'" The Daily News story at the time said Merlino pleaded guilty, but Peruto says what actually happened was that he answered "guilty" when the judge asked for a plea and Merlino remained silent.

That was then. Things change.

Why the change? Veteran defense lawyer Fortunato Perri, who has represented a long list of alleged bad guys, says: "Based on the case he was facing, I'm sure they made him an offer he couldn't refuse."

I thought that's what the other side did, I say to Perri, who laughs.

Merlino reportedly will get up to 16 months on a single gambling-related count.

Longtime criminal defense lawyer NiaLena Caravasos represented Merlino's codefendant, Frank Gambino, in a 2001 federal mob trial in Philadelphia. Make a deal? No dice.

"Mr. Merlino, along with my client and several others, chose to go to trial because we felt that we could win the major counts against us — which, indeed, we did," says Caravasos.

In the latest case, she says, admitting to the minor gambling count was worth it to make the serious racketeering charge go away.

That was pretty much the deal, I'm told by Merlino's current lawyer, Edwin J. Jacobs Jr. After an earlier mistrial, federal prosecutors and Jacobs agreed on a single count that would be "appropriate," in his words.

"In my 45 years of practice" in New Jersey, the Atlantic City-based Jacobs says, a settlement is negotiated "in 94 percent of the cases. Only 6 percent go to trial."

Yet in all the other cases in which Jacobs represented Merlino, they did go to trial. "Those results speak for themselves," says Jacobs, referring to a high win percentage.

During the '80s and '90s, Merlino made frequent appearances in my Daily News column, and during much of that time I lived in South Philly and was married to a relative of his. Jacobs advised him not to speak to me now.

Merlino now makes his home in Florida, says he's out of the crime family business, and denies running the Philly mob by remote control.

He is scheduled to be sentenced in September. If he goes to jail immediately, he'll probably be out before 2020. Before past incarcerations, he's talked about using time in the stir to work on his physique. The dapper Merlino, who favors form-fitting fashion, is no longer skinny, but kind of ripped.

Doing time is one way to save on gym membership.