With the observable strict correlation between brain process and subjective experience, including the creation and recalling of memories, how can one claim any aspect of the mind can survive without the brain? Even people who remember coming back from the dead are doing so with their brains, which means those memories were created in their brains as physical patterns either during the cardiac arrest called 'clinical death', in which case it is living brain activity, altered state as it may be, or afterwards, which can easily be explained away as the brain creating a false experience as it 'recalls' it. There'd be nothing to prove with the tunnels of light and seeing people they knew.
Out of body experiences on the other hand could be proven, if someone claiming them could give exact information about events they could not know about through any way other than going through walls to see while in trance. Experiments to determine this can be easily designed if the spiritual wanderer can enter the state at will, which they either claim they can't or that the presence of skeptics is ****ing up their mojo. So far, all experiments designed to atest the existence of paranormal phenomena have turned out squat and using data from non-controlled situations is gonna lead nowhere as there is a number of variables to acount for such as cold reading, individuals learning of events after waking up (which will be virtually impossible to control for), coincidence, vague descriptions of common or easy to predict events, the want to believe commonly found among parapsychologists, etc.