Matt Damon made a pact with his wife not to spend more than 15 days apart.

The 'Elysium' actor misses his wife of eight years, Luciana Barroso, and his daughters - Alexia, 14, Isabella, six, Gia, four, and Stella, two - so much when he's away working, the couple have made a promise to never be separate for more than a fortnight and a day.

He revealed: ''With my wife, we've established a rule of having 15 days apart maximum, and we never break it. However ... I've actually just broken it by being away from her and my daughters for 16 days, it was way too long.

''From the age of 40, time becomes precious, and any separation from my family is very hard.''

The 42-year-old star also opened up about his 'bromance' with long-time collaborator Ben Affleck, claiming he is one of the most important people in his life.

Matt - who co-wrote and starred in the Oscar winning 'Good Will Hunting' with Ben - told French magazine Madame Figaro: ''We're neighbours in Los Angeles, our wives see each other a lot and we're constantly working together, surrounded by our close friends and collaborators who help us with all of our projects. His opinion is very valuable to me.''