I desire to know when self-knowledge is “attained” (liberation, enlightenment, self-realization) — is it gradual OR an immediate event.
And is it completely permanent?
Attainment of self-knowledge is both instantaneous and a gradual process.
The recognition of one’s true nature as pure, limitless awareness takes place instantly.
But the process of purifying the mind through karma yoga, devotional worship, meditation, and energy management usually takes time. Realistically, several years.
Also, even after one has gained self-knowledge (realized one’s true nature as not being different from the TOTAL) — the process of fully assimilating the knowledge takes time.
Because self-ignorance is so deeply ingrained in us, it does not suddenly vanish upon our recognition of its falsity.
And this is why it's nonsensical someone claiming they're enlightened. So what! Many sincere devotees are. The real work is deepening oneself in the knowledge. This takes time.
Our habitual mental tendencies and limited thought patterns will continue to arise in the mind until they are completely nullified by self-knowledge. Or until one is AS convinced that I am Awareness (aham brahmāsmi) — just as one was, once upon a time, convinced that I am the body-mind-sense complex.
Once the old erroneous notions have been sufficiently muted, there is no going back.
Thereafter, even if the old voices call out from the nether regions of the psyche, one pays them no heed — recognizing that they are simply hollow epithets. Consequently remains steadfast in one’s true identity as Awareness (brahman).
Simply put, once removed — ignorance doesn’t return.
Now that you know that the sun doesn’t actually rise and set, but that it only appears to do so due to the earth’s rotation.
There is no chance of suddenly reverting to the erroneous belief that the sun is rising up from below the Eastern horizon at dawn, floating across the sky during the day, and finally plummeting below the Western horizon at dusk—despite the fact that appears to do so.
Similarly, once you know that you are limitless awareness (sat-cit-ānanda) — you are not going to start identifying with the body-mind-sense complex again — despite the fact that you will still be associated with it.
What’s more, Self-knowledge differs from knowledge-of-objects, in that the Self is not an object and, thus, Self-knowledge is not a matter of having accumulated a store of information that has to be remembered.
The Self is you.
You are the conscious “light” in which all objects are seen or by means of which they are known to the mind.
Thus, you are always present in every cognition.
Though you cannot be seen, you are that by means of which all else is seen (experienced in any way).
While an object or batch of information can be forgotten in its absence — you cannot be forgotten because you are never absent.
In fact, it is only due to your unremitting presence that the absence of any object — or even all objects, for that matter, as is the case in the deep sleep state — is known.
Once your true nature is recognized, therefore, it need not be remembered and, hence, it cannot be forgotten.