Note: I'm not enlightened. My knowledge is scriptural, and as such is only intellectual.  Dear @gswva  Because of law of karma(Tendencies, conditioning, behavioural patterns, Influences from others & society, etc..) - Once every bit of karma is burnt off including prarabhdha and there is no individuation any more, that'll be the end of that individual.  Karma is that fuel which keeps individuation going on.  Karma is generated through identification with the body / mind. Any form of identification which is of the nature of ego with the sense of doer-ship creates karma. As long as there is a karmic(cause & effect) chain binding you to some reality, your individuality is safe. Because, even if you get enlightened, the Prarabhdha Karma - 'The fructified karma which determines the experiences of current life' will not get dissolved until the current body dies. Because if it did, the body along with individuation would die the very moment enlightenment happens due of lack of any binding mechanism(karma) to bind it to duality. As to how the initial karma gets generated, there are varying opinions. I have some speculation on it. But, because of lack of direct experience, not so sure about it my self. Also, not sure even if enlightenment might make you understand it. Perhaps samyama on karma might help understand it. Brahman doesn't split into anything. The apparent world is just a projection with-in Brahman - like water seen in a mirage. Even when the projection is happening, there is no change in Brahman(Just like a mirror, even though showing the entire world with-in itself, doesn't change its own state).  These projections will keep happening with infinite realities with infinite Jiva(s)(living entities) emerging out and dissolving continuously. But, any PARTICULAR ENTITY with its own 'ego and experiences' having once merged into Brahman will never come back again.  "But, I am of the opinion that even after such merging, if prompted by some agency in duality, which has knowledge of said individual, that individual or even a whole reality of a universe can be brought back".  There is no self in Brahman. Brahman DOESN'T 'WILL' or 'WISH' to create anything(Willing and wishing are only for the creatures with a 'mind and ego' with-in duality. Brahman is beyond such concepts and is beyond Duality). Just like wetness and fluidity are intrinsic to water; Similarly, the nature of reflecting 'mirage like projections' of realities with-in itself is intrinsic to Brahman.  Such projections are what we refer to as 'Creation / Universe'. Brahman has infinite of such Creations / Universes with-in itself. Each of such universes exist within the mind of an individuated atomic-particle(Jiva - PRIMARY CREATION) of Brahman as an imagination/dream-like-projection with-in that Jiva(living entity) - whom we call as god or creator of that universe. These jivas are like mirages without any separate existence apart from Brahman. Cosmic universes(SECONDARY CREATION) experienced with-in Jivas are like water seen in that mirage. (Mirage and Water-seen-in-it are both in truth Non-Existent). (Scriptural Description along with my *own opinion* to clarify the Scriptural Description): With-in each such universe/reality, infinite other universes/realities are created by the jivas who have died in it *and are creating them through mental projection in their after life states / In states of deep meditation, either conciously or unconciously(Just like we do in our dreams). Some of those projections may intermingle with one another and function as one single universe/reality, with many such intermingled universes/realities in existence. While some completely isolated from others as separate universes/realities. Having once come into existence, being supported by Brahman; these universes/realities continue to exist even after the destruction of its parent universe i.e change in state of that jiva or liberation of that jiva who is projecting the parent universe with-in the higher order reality. *   With-in each of them, infinite other universes/realities exists. This cycle goes on ad-infinitum with-in them. We are living in one such reality/universe, whose nature is that which we experience in it. That's why reality as a whole is NOT JUST INFINITE IN SINGLE DIMENSION. BUT, INFINITE IN INFINITE DIMENSIONS. If you are to write it is as a mathematical equation, you can write its as Infinity(Infinity(Infinity(Infi.....))))))...  infinitely.   Not all experiences are neutral, There are literally infinity of experiences that can be had, ranging from suffering, to neutral, to unimaginably exotic realities, full of joy and happiness, stimulating all kinds of emotions and blissfulness with infinite variety to infinite degree. Because, Brahman is not limited by anything as it is the very source of everything. The human body/mind cannot grasp all of these realities from its current state, for it may not even have the faculties necessary to experience such states.  No experience is permanently the same. Even with-in same reality experiences keep changing.  "Just as karma, such is experience". Infact, some devotional schools of Bhakthi path doesn't even like Non-Dual liberation, and it is considered by them as a permanent suicide. The devotees after attaining a liberation of a dual type, experience going to imaginary heavenly abodes(one of the universes/realities mentioned above) of their imaginary gods(which are experienced as real - Just like this imaginary reality by us) and enjoy heavenly delights with no trace of any suffering, which is far more exotic and enjoyable than any earthly existence. For this reason, not everyone wishes to dissolve their individuation.  So, Non-Duality is not the only game in town. May be after Non-Dual enlightenment, one need to learning how to develop purified ego once again to furthur generate more sattva karma to keep the individuation intact. Even Ramana Maharishi who taught Non-Duality worshipped Arunachaleshwara. Ramakrishna Paramahamsa who taught non-duality to Swami Vivekananda worshipped Kaali. But, what type of liberation they attained I do not know.
My Opinion:  To maximise life's potential and blissfulness and swim constantly in variety "Non-Duality is to be Realised and Individuation is to be Maintained".