After a human's body dies and the soul leaves it, is there anything strictly keeping the soul from staying in this reality indefinitely? My first thought in regards to this was that death is like dreaming, so the mind would naturally 'drift off' in a trance state. But in the vast majority of these NDE accounts:
http://nderf.org/
The person reports feeling very lucid and hyper-aware, which is the opposite of what most dreams feel like. (However, this could just be because the physical body can still be used as a reference since it hasn't fully died yet even if heartbeat etc has stopped for a while).

So I'd think if this hyper-aware state was something that could be maintained one could will themselves to stay here to continue to exert influence. However, in Robert Bruce's Astral Dynamics he states
>During the final moments of death, most of the dying physical body's etheric matter is rapidly transferred into its newly forming etheric-plus/real-time body. A transfer of residual etheric matter also appears to continue, albeit far more slowly, for a few days after death has occurred, until everything left within the physical body has been transferred into its brand-new etheric-plus-real- time vehicle.
>The large amount of etheric matter (pure life energy or vitality) released during the death process sustains the integrity of the etheric-plus/real-time vehicle in the fully awake state. This holds it (plus the animating spirit) very close to the physical dimension (often) within the real-time zone.
>the second death can be delayed only if the spirit finds some way of replacing its steadily shrinking store of etheric matter. This can apparently only be done by close association (touching and hugging) with living beings with whom the spirit has an empathic relationship, leading to an etheric-matter transfer from the living into the deceased spirit's etheric- plus/real-time body.
Of course Bruce really isn't an expert on this sort of stuff and his frameworks tend to be rather elaborate. But if this were true it would introduce a problem for someone wanting to do this.