I know it is odd... but in fanfiction usually everything is unnecessarily angsty and people are acting like idiots in unrealistic ways OR they are unrealistically perfect in their relationship (constant erections in older men, multiple male orgasms... perfect love and understanding)
This was So REAL. People DO this. Especially if you are nearing a landmark birthday or such... When you are married you DO start to become annoyed by all those little things over time.
I LOVE how you fixed it. It was perfect and very mature-Harry.