If you haven't seen Bachardy's film from 2007, "Chris and Don: A Love Story", I highly recommend it. It was released on DVD last month.
The story mirrors my own experiences (my first partner was 31 when I met him at age 18), but in Chris and Don's case the age gap was much larger. The film explores the pitfalls inherent in this kind of relationship, even when both parties are madly in love with each other.