Eternal Love Triangle

Eternal love triangle is an expression which if taken literally means that it lasts eternity. It would be fun for sure – especially if combined with immortality and eternal youth – 'accessories' which are scarcely possible at least in our current mortal and aging reality.
There are no eternal triangles just as nothing lasts forever. However, we can apply the name 'eternal love triangle' to the situation when love triangle takes very long time to fall apart and turn into something adequately conventionally constructive – either a couple without odd man out or just three single people soon-to-be-ready too look for another – more successful relationship.
There are situations, for example, when a husband is into a long-term affair with his young lover. His wife knows about it but prefers to keep it on the low for this or that reason. As a result – he is happy to be in this situation, his wife is suffering, his lover is violently happy which is not 100 per cent happiness ya know.
Or, for instance, the case with Ryan, Bryan and Ann. She doesn't know who to choose and leads both by their noses and wraps them round her little fingers simultaneously or one after another. Their triangle starts acquiring the figurative name of eternal as a result – just a draggy love affair which brings nobody complete happiness, unless some of its participants are very ignorant about the trianglish situation...