Whether or not two people are HAPPY TOGETHER is what determines whether theit relationship is healthy or unhealthy. If you disagree with that, then you don't know anything about relationships. Period.

NOTHING is healthy or unhealthy for EVERY relationship of any sort. It all depends on the needs and desires of THE INDIVIDUALS involved, and whether they are being met sufficiently.

Period.

If something works for both partners and makes them both happy, then it's good for the relationship and it's HEALTHY. No matter what it is. Period.