What would happen if the main flame of consciousness was transfered to the astral body and never came back. What would happen if a person astral projected and just decided never to come back to their body? Would they fall into a coma? Would they die?

As for the silver cord interpretation, I think that is the mental manifestation of the concept of being tethered to the body. I am sure most people like their body and mental concepts manifest physically. A lot of literature is filled with that concept. Couple those two together, it manifest. When I astral project, there is no cord. In fact I am not aware of my physical body. My body has been slapped, punched, pinched, etc and that did not even register to me while I was projecting. My perception of time is skewed, so I spent what seemed like to me a short time in astral mode, but in actuality was about two days. My family freaked. It was like I was asleep, but they could not really wake me up. What was even creepier is that I often sleep with my eyes open. The same thing happens when I am projecting my consciousness away from myself when I am remote viewing, or scanning a person or an object, or managing mental links anf backtracking. It is as if I lose all connection to my physical body. I am no longer aware of what is going on.

Anyways, what would happen if I lost track of time and did not return for a while. What would happen if a person just decided never to come back? Would their body be somewhat comatose like mine was or would they simply die?

I'm sure "you" would "die" at least in the traditional sense. Your physical body, lacking any animating force would cease functioning, but on the plus side you'd be totally conscious of where you were in the astral. My take on it is that the opposite happens to people sooner or later, the physical body dies and the subtler body(s) are freed from it. I've only heard of one case where that happened to an astral projection addict, a woman died in her sleep because she spent too much time there and supposedly lost connection with the physical; she was contacted in the astral later by her friends and they worked out what had happened. I suspect it can't happen without you choosing to have it occur, or perhaps fearfully obsessing about it to the point of death.

I wonder if an "empty" body could host a walk-in...? Or be possessed by some entity by force?

Something like happened. In my experience, the entity hijacks the consiousness and uses that to take control. They normally worm their way into your mind and take over your personality by warping it, or suppressing the person's original. If there is no consiousness present, there is nothing to hijack. They could intercept the person's consiousness in astral form and use that to take control. What happened in my case is that the entity simply phased through my physical body. It would go in and appear on the other side, get frustrated and try it again. I was watching from above with a little amusement. In a different more extreme case, one entity got blasted out. A fragment of me had gotten ejected somehow, I am not sure if it was me or something else, but a small piece remained. It tried to worm its way into the divided me and got forcefully blasted out. It was like it hit a field and rebounded.

That is not the case with most people. A copy of the consiousness is copied into the astral form. At worst, in those situations, the consiousness is copied but split a little bit. That weakens the master version and makes them more susepctable to being influenced by outside forces or entities. A mentalist can be overshadowed by the mental stuff of another person, so in that state they can be more influenced by others thoughts and emotions. I actually still where the mental scars. An entity tried to overshadow me in that way and I still have some of its mental imprints in me. It was trying to get me to take on enough of its energy and emotions, while my barriers were down in that state, to become somewhat of a double of it. It was going to use that to jump into me. It was attempting to change my mind into a copy of it. It half way went through...

Some entities attach. They attach to you when you are in astral form and ride back in with you into your physical body. They gain a foot hold and spread throughout your mind. Most of the time its more of an influence or an overshadowing. Since the consiousness is the gateway to these things, that means a gateway is not present if the consiousness and/or subtle bodies are not there. I have had some try to take me over by finding me on the astral plane and trying to attack me. I have had some attack me while I was sleeping. Everyone projects at a low level during sleep and mental barriers are normally lowered.

Anyways, an entity can't hijack the body if no one is home.

Two things, though. That would mean that it is possible for people who do not have a strong enough attachment to their body to die while astral projecting, and if they simply chose not to come back, would that not be a metaphysical form of suicide?

Like wise

Astral projection is like meditating while you're holding your breath. It requires focus and you can only do it for so long. The human consciousness is capable of controlling the body to a point. When the body is in imminent danger, like you hold your breath long enough, the primal mind takes over and forces the body to breath. Likewise if you breath too fast too long you can cause yourself to passout, yet another mechanism to ensure the body's survival.

Of course it is entirely possible to circumvent these functions. For holding the breath it is possible to practice at it and be able to hold it longer, still only to a point. In the case of astral projection one might use certain drugs that increase one's ability to remain on the astral plains and its possible to die while there. But death from AP is rarely caused by a person willing themselves away from their body, I'm don't think its impossible. The thing is if people astral project naturally, much as we dream, then people would be more prone to just wander off and more deaths would attributed to such dream like states. Dying in one's sleep happens very rarely. Usually its an external cause like an ulcer, heart attack, OD or accident. Its also possible to be frightened to death while AP. But there is still that natural mechinism that for the most part holds people in check.