Multiplicity of conscious existence
The concept of itomultiplicity or some modified version of it, is the most likely correct theory dealing with conscious existence in our universe. The other options are nonexistent, singularity and universality. Itomultiplicity means that there can exist different versions of each person's consciousness that he experiences as his own. So right now there could be many versions of you with your ixperiencitness.
The biggest argument against the multiplicity of consciousness existence is the itomultiplicity paradox. The paradox is that if I am actually someone else as well as my current real self why do I not experience their life like I am experiencing this moment reading this sentence, Since I am not experiencing what they are, I am clearly not them. Consequently since I am clearly not them nor they me, multiplicity is surely false!
The first answer to this is that what we are consciously at any moment is produced by the structure and functioning of the brain. The structure and functioning of the brain is always changing so is the consciousness. But usually the ixperiencitness is not changing or changing very little in a human body. The consciousness does not change much if the structure and functioning does not change much. The brain is always cycling in it's processing from the smallest level of ions passing in and out of the neuron cell wall to the neurons repeating firing. The cycling on the more complex levels can have small variation that can repeat a conscious experience or have it be slightly different. The functioning that has happened at each part of your life is not likely to be repeated exactly at any time. If we imagine traveling into the future or past and observing ourselves at this time it will become very clear that we had a different consciousness at these different times than we do at this moment. If you could actually travel into the past or future and see yourself you would not be experiencing what they are experiencing. If it is a requirement that you have to experience want previous or future "you" experiences for them to be you they could not be you because they do not experience exactly what you do. Then the only real you is this very moment and all other conscious moments of your life belong to many others that are not you. It maybe that people only exist only for a moment before they are gone for ever But we do not want to believe this and there is really no proof that you ixperiencitness changes from one moment to the next.
Luckily the ixperiencitness concept makes understanding the conscious existence over time. If any body has your ixperiencitness then they are a case of conscious survival or life after death for you. The ixperiencitness concept is not an all or nothing concept. It is a continuum concept which means there is a percentage identity of ixperiencitness. For most of our lives we have the same ixperiencitness but there is a transition at early development and eventual death. There are also any major change in the structure and functioning of the brain like a brain injury that can happen at any time in the life of a person. If half of the brain is removed it is likely there will be a major change in consciousness produced by that brain and a very likely a percentage change in the ixperiencitness.