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Tim McGraw and Faith Hill have been working together for more than two decades, but they are only now releasing their first-ever duets album.

Last week, the couple started the third installment of their very successful Soul2Soul World tour.

"I haven't been on a stage like this in 10 years and that is no lie," Hill said of the tour. "I can tell you right now I am fired up."

During an Associated Press interview with the couple before their rehearsal at the Academy of Country Music Awards in Las Vegas earlier this month, Hill and McGraw were giddy with anticipation.

"She's ready to turn it loose," McGraw said.

"Age is not an issue," added Hill, who together with her husband will be turning 50 during the tour that runs through October.

The Mississippi-born Hill and the Louisiana-born McGraw fell in love when she opened for him on his 1996 Spontaneous Combustion tour and they married that year.

In 2000, the first Soul2Soul tour grossed $48.8 million, making it the best grossing country tour in North America that year, according to Pollstar. The Soul2Soul II tour was even more successful, grossing $88.8 million in 2006, and made it the 3rd highest grossing North American tour that year.

McGraw credited their success on the road to the fact that they are very different singers who push each other to expand their ranges onstage.

"Faith, I would say, is more of an R&B, sort of gospel-inspired singer," McGraw said. "And I think I am more a '70s rock, arena rock, Merle Haggard meets arena rock kind of singer. She brings me a little bit more to the R&B side, and I bring her more to the arena rock side, and I think it creates a sort of magic."

Their first duet together, "It's Your Love," was on McGraw's 1997 "Everywhere" album, which was followed by "Just to Hear You Say That You Love Me," from Hill's multiplatinum album "Faith." Since then, they have had several popular duets, including their latest, "Speak to A Girl," which jumped into the Top 10 of Billboard's Hot country songs chart after they performed it on the ACM Awards.

But they say they don't always agree in music, or in marriage, but McGraw said commitment is key.

"Look, there is no secret," Hill said. "Either you like one another or you don't. You want to stay married or you don't. You work at it, or you don't. Simple as that. It is not always easy and there are moments that are rocky."

"But you don't walk away," McGraw said.

"I would rather live a life in rocky road ice cream than vanilla any day of the week," Hill said. "Honestly, vanilla gets boring after a couple of days."

A smiling McGraw adds: "So I am not vanilla!"

The Associated Press contributed to this report.