Thank you, everyone for your insightful input!
Well, I have decided then, that anything that we imagine has it's own reality in and of itself, but it can disappear the same as a Belief System Territory will disappear once all members have left it. So, I think that 'imaginationland' must work in the same way, then.
Kind-of like what Spooky mentioned here:
"However, these creations remain dependent on their creator (I guess it's possible subconsciously), or at least someone who continues to invest thoughts/energy on maintaining this creation."
So, when no more people continue to invest thoughts and energy on said 'creation' it would perhaps 'wink out' like any belief system territory with no more 'believers'. But, just because it is an 'illusion' of our own making would not make it any less real to the members of that reality, since our physical reality is the same for us. Like what Lights of Love mentioned here:
"What I usually call God Consciousness or the One Consciousness is the foundation of all reality. Primary reality. All other realities including ELS are secondary realities derived/evolved from primary reality. A hologram would be one example of how this seems to work."
So, in other words our life system here is just as illusory to the 'spiritual world' as the creations of our imagination are to us. But we are 'real' to ourselves, are we not? So, I think our creations would be just as real to themselves, as well, because we are, after all, Co-creators with God.
So, anyhow, boiling back down to the main point of this thread I had in mind, was that if the worlds in which we create, or collectively create have a reality of their own, like an illusion within an illusion, can those worlds be visited by us?
Thanks, again, everyone for the excellent input!