I have always reasoned, that since The Way to nibanna was The Noble Eight Fold Path, that it was through living one's life in accordance with the path that unbinding, release, and attainment was achieved.
My current reasoning with what little understanding I have of it is that the luminous mind concept to me is a mind without defilements, free of hindrances, fetters, shackles, which is but a result of living one's life in accordance with The Noble Eight Fold Path. I imagined to be like a pane of glass clean of all dirt and dust.
Another way that I have reasoned is that if a person is racked with pain, let's say due to a painful disease which attacks and inflames the pain sensors of the body, and the source of the disease is removed, one is pain free, and by contrast in an ecstatic state. No joy may be present. No sensory ejaculation of pleasure so to speak, but simply recognition of the cessation of racking, intractable pain. Therefore: a luminous mind, in a state of luminous equanimity. These states are but temporary conditions, because exterior conditions, which initiated the pain can change at any time, and therefore not nibanna, which is a permanent state free of all sensory consciousness good, bad or indifferent.
Therefore, why are such states of luminous mind, and luminous equanimity ever the goal? Nibanna is the goal.
What Makes an Elder? :
A head of gray hairs doesn't mean one's an elder. Advanced in years, one's called an old fool.
But one in whom there is truth, restraint, rectitude, gentleness,self-control, he's called an elder, his impurities disgorged, enlightened.
-Dhammpada, 19, translated by Thanissaro Bhikkhu.