llevar [número cardinal] años conviviendo) en pareja

They have been living together as a couple for five years and are very happy.

This phrase highlights the fact that a couple has been living together for five years, emphasizing their happiness during that time.

We have been living together as a couple for three years and have learned a lot from each other.

Here, the speaker shares their experience of living together for three years and the personal growth that has resulted from their relationship.

My parents have been living together as a couple for ten years and always support each other.

This sentence conveys the idea of a long-term relationship, emphasizing the mutual support that has developed over a decade of living together.