This makes me think of something. When we go to sleep we get more and more tired and then we feel the deep sleep engulfing us. Like you said, the feeling dying people get is the feeling of a deep sleep engulfing them as they are tired. This could mean dying people go to the same place that those who are sleeping goes too. This is what i believe. Both go to the same place. Not saying this is always the case though. But i think this is often what happens. In other words we could say those who dream goes to the spirit world several times at night. I have believed for long time that people astral travel to the spirit world when they sleep. Interesting... this make me more curious.