Here is my list: (Share yours.)
1. You can fart in front of each other.
2. You can pee in front of each other.
3. You don't seem to get tired of kissing each other.
4. You enjoy being together.
5. You don't fight often and, if you do, you know how to communicate and work through your fights/disagreements/differences.
6. You have respect for each other.
7. You have the same interests/values/goals/hopes/dreams.
9. You have the same views and beliefs.
10. You both want each other for the long-run.