Merle DiVento and her husband, Larry, are in their 60s, but they spend a lot of time playing school, making art projects, and reading board books.

It's the dream job they retired for: caring for granddaughters Gianna, 4, and Jewel, 15 months. Still, for Merle, who taught mostly kindergarten for more than 36 years, and Larry, now working at his at-home framing business around his babysitting duties - it's "exhausting."

The Mount Laurel couple wouldn't have it any other way.

"Now we build our lives around theirs," said Merle, aka "Mimi," whose commute is a minutes-long car ride to their daughter's home. "Grandparenting is even better than having children."

Although grandparents have helped raise their grandchildren for centuries, a growing number of people are aligning their retirement planning specifically for babysitting. Like the DiVentos, they are healthy, financially comfortable, young at heart, and eager for a do-over to help raise children with a bit more perspective the second time around.

According to a 2015 study published by the National Bureau of Economic Research, women are more likely to retire after the birth of a grandchild than women who have no grandchildren.

Financial incentives like pensions and health insurance are the most important factors affecting women's retirement decisions, said one of the study's authors, Robin L. Lumsdaine, who teaches international finance at American University's Kogod School of Business. But she was surprised by the extent to which having a new grandchild influenced women's decisions - an 8 percent increase in probability.

Amy Goyer, an AARP grandparenting expert, noted this generation of child care providers is different:

"Now we have grandparents who are the most stable financially of all the generations in their family, so they may have the ability to retire earlier," Goyer said. "Boomers have changed the way that we age - they are much more active and have a different view of aging and what I can do in my life."

Many, such as Merle, 65, appreciate a second chance after having worked throughout her own children's childhood - "I needed to work because we were a two-income family." Now that daughter Ashley Biddle, 31, a pharmacist, and son-in-law Matt, 31, an account executive, also rely on two incomes, Merle is able to lend a helping hand.

But money wasn't the most important factor, Biddle said. "It was the only way I could leave the house and go to work with a clear conscience. Knowing they would be in good hands with my parents made it OK to leave."

Biddle appreciates her mother's teaching experience, and she gets a kick out of seeing the girls with their grandfather.

"When we were parents," said Larry, 68, who goes by Pop, "I would be at work and Merle would be with the kids and I would miss all that."

Pop delights at the funny things Gianna says, like the time he invited her to eat on the couch but Gianna forcefully pointed out that was a no-no in the Biddle household.

"I said, 'Is your mom here?' " recalled Larry. "She said, 'No,' and I said, 'Well then, we're going to eat on the couch.' Then she tells me when her mom comes home she's going to tell on me."

Merle insisted she's a little wiser the second time around, having learned from mistakes she made with her kids. Now, she tries to be more consistent - although she says she's also more lenient "because I think that's what grandparents should be."

And for Biddle, that's the one drawback: Fun-loving grandma who showers them with gifts may not abide by mom and dad's rules.

Maia Noeder, a pediatric psychologist at Nemours/Alfred I. duPont Hospital for Children, has seen an increase in extended families sharing child-rearing responsibilities. Over the last five years, the numbers have gone from just a few to as much as 25 percent of her clientele.

She often sees conflict between parent and grandparent because "there are two sets of disciplinarians, and their ideas aren't always going to be in alignment."

But she knows of research that shows grandparents get cognitive benefits from caretaking: "Taking care of grandchildren who are cute and adorable and fun also helps reduce symptoms of depression," Noeder said. And for parents, "It's much more comfortable having a grandparent where you have more control over that care."

Yet, Goyer of AARP urges grandparents to be sure they are ready to take on a new job. She advises them to continue to follow through on their retirement dreams, such as traveling and pursuing hobbies, and to make sure their children aren't taking advantage.

For Belinda G. Rosen, the decision was a no-brainer.

Though Rosen, 62, thought she might work another couple of years as a special-education teacher in Camden, she realized the timing was right to care for her granddaughter Aria Cohen, born in August.

"I want to go out on top," said Rosen, of Medford, who will begin full-time babysitting duties in January at her daughter's house after she officially retires in December. "I like that I'm retiring to another job."

Leaving her beloved job as an aerobic dance teacher of 30 years was a difficult decision for Cecelia Handza, 62, of Voorhees.

But when her son and daughter-in-law in Philadelphia asked her to help care for her grandson due Aug. 26 - for financial reasons as well as a desire for their child to have that family connection - Handza felt it was a good choice.

"Children get a different view of the world from their grandparent," she said, "than they do from their parents."