Have you noticed that when people of a certain age come together that the bulk of the conversation has something to do with health? High cholesterol, diabetes, vision and hearing, aches and pains and limited mobility. They compare medications and what doctors have said about the various issues.
Often the condition of teeth pops up, with some bragging about a lack of cavities while others bemoan having another tooth removed.
They discuss what types of foods are now prohibited and that they miss or share recipes for low caloric foods.
On and on they go, often circling back to original topics because they forgot what’s been hashed over.
Your characters, when they reach that age, would do the same. Begin by establishing what health issues your characters have. It would be beneficial, for conversations sake, if they didn’t share the same ones. They could have the same doctor, but perhaps it might add complexity if they did not. The same would be true for the medications that they are taken.
Picture what would happen if one character believes his issues are worse, or more important. He trivializes hers, minimizes the severity of her ailments and maybe even contradicts her doctor’s recommendations.
Interesting, tense-filled conversations arise that could lead to the dissolution of the relationship.
Have fun with this one.