I am no buddhist, but I do believe that mental states tend to be the result of habitual ways of thinking, that is to say habitual ways of perceiving, judging, and reflecting. If one tends to habitually judge in a preconceived, unmindful way then bigotry is likely to be the result. Contrarily, if one has the will to eliminate all prejudice then the perfectly magnanimous, clear, and attentive state of mind is likely to be the result. As has been observed above, these mental states are inherently transient- if one acquires different habits of thinking, then one's mental state will change with it. Robert Anton Wilson wrote, "The mind and its contents are one and the same."

For me, (again I am not a Buddhist) enlightenment is that state of mind that arises from habitual openness, attentiveness, and identification with all else. Enough practice and the state of mind begins to reinforce itself. So in a sense, enlightenment is eternal, if one manages to retain the habit.

I do not know how different schools or traditions of Buddhism tend to understand enlightenment, but I think I have a good understanding of enlightenment in the tradition that I see myself as a continuation of- current neuroscience and westernized mysticism as it were.