How did they make it 40 years?

This past weekend my family and I had the honor of attending a bbq celebrating Bev and Frank Bradley's 40th wedding anniversary! While the bbq was crazy in itself with 11 children running around all under the age of 8, the majority under the age of 5, it really got me thinking! It is rare to find couples that have stayed together for such an incredible amount of time, and I am now questioning, what do you think it takes to make it 40, 50, 60+ years of marriage? I am excited for the day that Andre and I can look back and say, "wow, it's been 20,30,40 years" and still be happy and in love. So what are your thoughts? What does it take, other than a lot of prayer, and chocolate for the wife HAHA!!!