Wanted to post a reply to this topic here
But since it was in the Classical Theravada section my response there wouldnt be in accordance with the rules, hence the new thread here
I think it is true that we can infer to a degree the nature of other existences by understanding those momentary states of mind that arise in this life and so I don't think it is wrong to emphasise this aspect. Bu I believe the Buddha taught the planes of existence with a view to the real nature of the world. I think accepting this doesn't have to make one terrified of future lives or hopeful of heavenly pleasures. I think it acts to force one more onto the present because one knows that life now - which is only seeing, hearing, tasting, touching, thinking etc - is no different from life in the past and it will be just like that in the future. It means one becomes intent on understanding this moment and how the factors of the dependent origination work their ways.
Specualtion about heaven and hells after death is just that, speculation. It leads one away from the present. Thinking of them as physical realms as well, i feel, leads one away from focusing on the true reality of them as mind states that are here. This was all Ajahn Buddhadasa was trying to do, get people to focus back on there here and now and stop speculating about the future (which isnt even ours anyway)
He wasnt the only one to say such things (of heaven and hell only being mind states)
As the The Supreme Patriarch of Thailand said
"His Holiness' view on Heaven and Hell
... His Holiness’ two books on heaven and hell are truly analytical view on the subject from a Buddhist point of view. As we are so familiar, in religious sphere, the concept of heaven and hell is a very prominent belief. In many cases, it becomes the goal of religious practice itself. On this very subject, His Holiness critically analyses that the very concept and belief of heaven and hell in Buddhism is a cultural influence of indigenous culture and belief. He states: (I quote) [b]‘the subject of cosmology appeared in Buddhism is clearly can be seen that it is not ‘Buddhist teaching’ at all but an ancient geography. The concept and belief about it was included in Buddhist Canon merely because of strong influence of popular belief of the time. Later Commentaries further explain about heaven and hell in a greater detail distant itself from the original teaching of the Buddha. If Buddhism teaches such belief on heaven and hell it would not be Buddhism at all but an ancient geography. Buddha wouldn’t be the Buddha who delivered the Noble Truth and ‘timeless’ message for mankind.’ (p. 1) (end of the quote) He then shows in his teaching that the concept of heaven and hell in Buddhism are in fact symbolic, representing the quality of mind and spirituality instead. One can be in heaven and hell in this very earth and life. No need to wait until one dies...*
What use can there be in speculating on heaven and hells after death, when all the work and attention needs to be here and now?