Linda Waud and Charles “Ben” Waud dated through most of high school and a year of college, then went their separate ways.

Shortly after they bumped into each other at their 35-year high school reunion, they got married. Since then, the Florida couple have been inseparable for more than two decades.

“Yes, this can be a beautiful life,” Linda Waud said.

More couples are rekindling high school and college romances, though not all of them have the happily-ever-after ending that Linda and Ben found. But newfound old loves are turning out to be long-lasting.

A study by Nancy Kalish at California State University, Sacramento, found that of the 4,000 participants who found their way back to old loves, 72 percent of them were still together.

That’s not all the ongoing study, which began in 1993, discovered. Fidelity also played a role.

If they were married at the time that they rekindled their romance, the success rate was just 5 percent, because one or both didn’t leave their marriages. For those who did leave their marriages, the success rate for their rekindled relationship jumped to 72 percent. And, if they returned to the first love they ever had, the success rate was even higher: 78 percent.

These rekindled romances appeared to be even more passionate than rom-com movies would suggest: 71 percent of those in the study said that their reunion was the most intense romance they’d ever had. They also tend to take off at warp speed.

“These romances are a lot faster: They meet for coffee, and then they go to a hotel room,” said Kalish, a professor of psychology.

It happened very quickly for Megan McDonald, who dated John McDonald in high school, but suffered from the breakup when he went away to college.

Over the next three years, they didn’t talk but constantly asked about each other via mutual friends.

When Megan bumped into John at dinner at a friend’s house, they realized they had to be together forever.

“We made the decision right then and there, and decided that if it was going to be real, it needed to be real, because neither of us lived in the same state,” Megan McDonald said.

They decided to date long distance for two years until they could rearrange their lives to be together.

Now, the couple, who live in Chicago, have been married for 10 years and have a 5-year-old and a 4-month-old.

Younger, more complicated

There is an unfortunate side of meeting an old love a few years or even decades down the line. Many are in new relationships, Kalish said.

The internet has made finding old loves very easy and very casual. A simple e-mail or Facebook message isn’t as suspicious as a handwritten letter or even a phone call, she said.

But that initial message can lead to another, which eventually could result in a meeting that ends in an affair.

“These people weren’t looking for affairs. They never cheated before, and they never cheat again,” Kalish said. “Before you know it, all the emotions come back, even for those in a happy marriage — they don’t expect it.”

Decades ago, old loves met mostly at reunions, most later in their lives, when their children were older. But today, they’re reconnecting when they’re younger because it’s easier to stay in touch or to find each other through Facebook or other social media outlets.

That usually means couples are bringing young children into their affairs.

But these aren’t the only issues to consider.

If the couple miss out on years of each other’s lives, they often feel resentful that they lost this time and that the other person gave those years to someone else. Many times, they can’t or won’t have children with their old loves.

Despite those issues, many couples make it work. But they need to realize that they’re different people than they were in high school, said Rachel Sussman, a licensed therapist and relationship expert.

“When we think back on those memories, especially high school and college loves, we were carefree and looking beautiful and thin and happy. And we have an idealized idea of what love looked like, and our brain naturally does a trick on us,” Sussman said.

Instead of thinking about any problems in the rekindled relationship, you think about your passion and how much better that relationship was than all of your later relationships, Sussman said. So you need to work hard to be realistic, and realize that there may indeed be problems in the relationship.

Common ground

But research has shown that the more you have in common with someone, the better the chances of succeeding in a relationship. It’s likely you have much more in common with your high school or college love than you have with someone you randomly meet online, Sussman said.

Sometimes, that’s exactly why these relationships have such great odds: The couple tried dating other people after high school or college and realized that the alternatives weren’t so great. They’d really clicked but gave up on each other because they thought they were too young, or because they thought they could find someone better.

But years later, they still haven’t found that person they invented in their heads, said Randi Gunther, a clinical psychologist, marriage counselor and author of “When Love Stumbles.”

Or maybe they married and then divorced, and were trying to figure out what to do next. And they started wondering whatever happened to their first love, who usually was a very pure love, free from the practicalities of financial or other restrictions.

The phrase “absence makes the heart grow fonder” could also apply here, Gunther said.

“When people fall in love from their hearts, and not from practical choices, those loves never go away, especially when they occurred when they were not yet bruised or cynical,” he said. Couples who reconnect describe it as “coming home,” she said.

But these couples still need to have real conversations about their lives as they are today, as opposed to simply going back in time, Sussman said.

“The early dates are really exciting because you’re playing catchup: You have those stories of what it was like to go to prom together,” she said. “But then, you have to play catchup and use the same criteria of dating someone new. Do you have the same life goals? Finance goals?”

Make sure you use the same strict dating criteria with your former love that you’d use with anyone else, Sussman said.

One thing you can skip? Giving your history. They already know it.