Explore the long-term ramifications of breast cancer on a woman's body image and sexuality. Toy with the idea of him having an affair with her best friend. Forget about it and then ignore them for awhile. Then have her have a sudden, unmotivating affair with an attractive but shallow colleague. Turn the lover into a nutcase and have the couple reconcile again.
Ratings are the bottom line.
If the storylines are good, the ratings will be good as well. Bad ratings are an indicator of bad storylines. When the ratings fall, I change what we're doing. Higher ratings mean to continue in that direction. But consistent, character-driven plots will always resonate sooner or later.