1. You got more attractive. It is now time to upgrade.
2. You are about to inherit great wealth and you don't want to share.
3. She doesn't find Monty Python
4. She is maddeningly underwhelming in bed.
5. She doesn't let you sleep with other people.
6. When she does the laundry, all your clothes comes out shrunken to the size of doll clothing.
7. She doesn't... well... you know...
8. You want to sleep with someone else.
9. When you were twelve, a gypsy told you that you would die at the hands of a lover...and you are starting to think this woman may be that lover.
10. The thrill is gone.
11. She laughs aloud at Dilbert.
12. She adamantly refuses to wear the Princess Leia slave bikini. (Cut the crap. You know that isn't just a fantasy for nerds.)
13. She once reminded you of a young Jean Simmons. Now she looks eerily like an older Gene Simmons.
14. She wants you to go vegetarian.
15. Somehow, between the beginning of the relationship and now...she got really damned annoying.