Intriguing subject. I tend to be a rather skeptical person about subjects like these because I prefer rigorous scientific scrutiny than just metaphysical interpretations of things. With that said, still want to keep an open mind about these topics.
When I was in my late teens, I had experiences during sleep that still intrigue me to this day. They did not feel like ordinary dreams at all. In multiple ocassions, I felt like floating out of my body horizontally, then rotating 360 degrees multiple times and then returning to my body. In at least another occasion, I felt like flying away fast to an unknown destination, only to rush back to the body when waking up.
I stress that those were sensations, so I am not suggesting that I really "left" my body. As said before I need to see more research and evidence on this to learn about it because I am not an expert on the subject. I just remember that the sensation was incredibly peaceful, safe and comforting.
I wonder why I have not experienced these once I reached full adulthood. I also wonder if what I experienced may have been impacted by hormonal changes during adolescence that may have influenced my brain activity. Anyway I will look into that further.
You described all that well.
That you didn't continue with your explorations into your consciousness by this method could have been any number of things, possibly but probably not so much a matter of the physical at that age, however, I don't know how dementia might later play into it. I'll let ya know or hopefully not haha.
A lifelong lucid dreamer generally and practitioner of dream yoga specifically for decades now, I've wondered if the extra (excess?) thinking during sleeping, particularly at that level of thought, mightn't have established enough neurological connections to help stave off any pending dementia of ageing, but I'm not aware of any conclusive research on that yet.
Western science is only about one or 2000 years behind the Tibetans on this so I guess I'll just wait and see how I do.
I have at times during this living nonsense turned off my dreaming and then turned it back on again, so I'd imagine you could still access it if you wanted, though these many years away might mean some work for ya. It could be that you stopped by lack of interest, by fears, by misunderstandings, whatever the case might have been. In my case, particularly the last time I stopped, was because I was so inundated with the consecutive deaths of loved ones that I was mourning in my sleep, giving me no rest whatsoever. I'd wake up with my body crying in convulsions. Not good. So I turned it off consciously. I had also turned it off unconsciously as a child for a few years from when my grandma died until it kicked in again when I was a teenager.
I've got just a few years on you but we're in the same cohort, so recall that when we were teens, there was very little info on this in the west. So keep in mind that at that time you might have had a lot of fears and certainly a lot of uncertainty which might have helped over time make you comfortable with your skepticism but at the time might have lead you to push away your experiencing of your mind in this way. It is all still there and I'd imagine you could find your way back to it were that your will.