When I think about retiring, probably sometime in the late 21st century, fantasies of the good life fill my head — fly fishing in Montana, traveling on the Orient Express, cocktails at the Eiffel Tower, hobnobbing with the hoi polloi at Swanky Franks dog house, and hiking down the Grand Canyon while my wife sits at the top, sipping gin and tonic.

All that excitement is going to cost a pretty penny, which is why I'm trying to save more and spend less before Social Security collapses.

I’m also trying to recoup thousands of dollars that went to finance my four daughters’ love of fashion, their college educations, their cars, their car insurance, their weddings and their phone bills. But as we all know, that’s the price tag of fatherhood. It’s like being on the board of Lincoln Center. You’re expected to give a lot for the privilege of taking a selfie with Placido Domingo in front of the fountain while he bursts into a vigorous rendition of Verdi’s La donna e mobile from Rigoletto.

But I recently learned from my wife — the same woman who will be sipping gin and tonic while I’m sweating and stumbling up and down the Canyon — that there’s been a change in plans. You see, she has her own spending priorities for the future and fly fishing isn’t on the list. She wants to put my hard-earned cash toward ... the grandkids.

We already have a room filled with cutesy baby clothes, onesies and twosies, or whatever those things are, piles of jeans, socks, sandals and toddler bowties. The little guys aren’t born yet, but they could be modeling for Baby GQ with the wardrobes they have.

I’m not a piker. I love my daughters and I dearly love my grandsons who are on the way and my one granddaughter who’s already here, but at this rate I'll be working until I’m 80, and I'll never get to ride on the Orient Express although I might salvage enough for a chili dog or two at Swanky Franks.

Journalist and grandmother Lesley Stahl, whose new book is titled,Becoming Grandma: The Joys and Science of the New Grandparenting, was on a Fox Business show recently and said, “Grandparents are taking over [paying for] the medical care, education and daycare of their grandchildren.”

Stahl, who is a longtime correspondent for 60 Minutes, calculates that grandparents today are “spending seven times more on their grandchildren than grandparents spent a decade ago.”

They’re doling out an estimated $30 billion a year, according to a survey by AARP, with many contributing to major expenses — 53 percent to education, 37 percent to living expenses and 23 percent to medical or dental bills. In addition, 11 percent have grandchildren living with them.

There are 70 million grandparents in America, and they control 75 percent of the wealth. An estimated 30,000 Baby Boomers become new grandparents every week, so it’s reasonable to assume that spending on grandchildren could do something Barack Obama didn’t do and revive America’s economy, not to mention raise the stock price for Buy Buy Baby.

Grandparents head 50 million households in America so they’re a voting bloc more formidable than middle-age white men or feminists, which means to say they should lobby Congress to make spending on grandkids tax deductible. This is a topic that Hillary and Donald should be talking about.

For years, I struggled in the salt mines so my daughters could have the trendiest fashions. I’d lie awake at night and worry, “Will they be stylish enough? What will the other kids say? Maybe if I got a part-time job as a tree surgeon, they could spend more on clothes.” At home, I was known as “Son of Santa.”

Then, they went to college even though in retrospect it would have been more lucrative for them and for me, if they became plumbers, electricians or landscapers. (One of life’s fundamental lessons is to always know a good plumber, especially if she’s a family member.)

I may as well forget fly fishing in Montana because when I retire I’m going to be splitting my Social Security check with the little guys so they can have money for Twizzlers and Transformers action figures.

On the other hand, if I get the little guys to mow the lawn and rake the leaves, I’d save money on landscapers. It would be a win-win. How old do they have to be before I can send them outside to do yard work?

Contact Joe Pisani at joefpisani@yahoo.com.