Bo Derek and John Corbett have been together for 15 years, which is an eternity by Hollywood standards. The two have never walked down the aisle, but they still appear to be the picture of love and happiness.

So, what's their secret?

Invision/AP/REX/Shutterstock

"We both travel so much, so for us, our favorite vacation place is home," Bo, now 61, told Closer Weekly. "That's where the romance is."

John, 56, added, "We enjoy each other's company; we make each other laugh. After 15 years we still hold hands; we still have barbecues with friends a couple times a week. [And Bo] still laughs at all my jokes even though she's heard them a million times. We just enjoy each other. I'm sad when she's not around."

The two are fiercely loyal to each other and he once told Wonderwall.com how to be faithful to your partner. "Don't let the lizard out of the cage," the "Sex and the City" star said when asked to give advice to those in Hollywood with a wandering eye.

INB / WENN

In 2015, the couple told "Today" they met via John's pal, who only introduced them because he was having a party and John didn't have a date.

"I said, 'I'm not dating anyone,' and he said, 'I'll get you a date, Corbett!' And he set me up with Bo," John said. "I was very intimidated!"

For Bo, who "hadn't dated in five years," the attraction was immediate. She said she liked him "instantly ... I kept saying to my friends, 'I'll wait until all the sparks and all that get going.' And it finally happened."

IPA/WENN.com

Bo, of course, was the apple of men's eyes several decades ago. John still gets recognized for his role in "Sex and the City." His faith, he said, keeps him grounded.

"I went to Catholic school for 12 years and I was an altar boy for about seven of those years," he told Closer. "I spent a lot of time behind the scenes in churches."

He maintained that he has a "strong belief in God" and describes himself as a "gospel and brunch kind of guy."

"Nothing says I love you Jesus more than gospel music and mashed 'potaters,'" he said.