Answer? None.
According to a study conducted out of Emory University, the larger the age gap between you and your spouse, the more likely your marriage will end in divorce.
The likelihood of divorce increases in direct correlation with increases in age difference; a 5-year gap means you are 18% likely to get divorced, a 10-year gap increases the odds to 39%, and a 20-year gap leaves you with almost 100% chance of divorce.
The full study results can be reviewed here: http://www.randalolson.com/2014/11/06/what-makes-for-a-stable-marriage-part-2/