Tim McGraw and Faith Hill in Nashville, TN on November 9, 2011. Credit: Jason Kempin/ABC via Getty Images

How do country superstars Tim McGraw and Faith Hill keep their marriage strong? Joint tours.

Unlike most top headliners, McGraw 45, and Hill, 44, had only one major demand for their upcoming shows at Las Vegas' Venetian Hotel: "It needed to work around our kids' school schedules," Hill tells Us Weekly of her Soul2Soul residency with her Grammy-winning husband (tickets from $95, ticketmaster.com).

"We'll be there for 10 weekends from December to April, so it's spread out." Adds McGraw: "It's so exciting."

While flying to and from the Tennessee estate they share with daughters Gracie, 15, Maggie, 14, and Audrey, 10 will be tiring, the country duo credit joint tours as the secret to their 15-year happy marriage.

"You have to walk this life together," says Hill. "And you have to like the person who you love."