Thirteen is lucky for Nicole Kidman and Keith Urban - that's the longest period of days they can bear to be apart.
Kidman reveals the romance is still very much alive in her year-old marriage, despite the media scrutiny and Urban's rehab stint.
And she puts that down to the fact her country star husband refuses to spend weeks away from his wife.
The actress tells Ladies Home Journal magazine, "We'll never be apart for more than 13 days, actually. Because he says, 'That's it. That's it for me. No more.' And I've never wanted to live my life apart from the person I love. So that's what we do.
"You can make that stuff work. It's what he calls, 'the old-man view', like when you're an old man and you're looking back, you try and see what's important."
Kidman admits she and Urban "found" each other at the perfect time: "I think we were two lonely people. I would probably say that two very lonely people managed to meet at a time when they could open themselves to each other."