Simon, I left mentally when I was 18, and sent a letter of DA at 21. Born-in here. (I shouldn't have sent anything or played by their rules, so that's neither here nor there.)
It's less a part of my life, for sure, though my whole family of origin is still in it. So no contact. Still has an impact.
For me, it's nothing like forgetting where it is or a vague recollection of the people etc as you wrote. I can't speak for anyone else, but for me it's all very, very vidid, even 30 years later. It's like it was yesterday. The people, the meetings, the assemblies, the sights and sounds...The smells of the cafeteria food at the circuit assemblies, everything. I can still see it, hear it, smell it, taste it... It's all there.
The beliefs, the Watchtower Corp, etc. It's all total bull crap. That stuff was packed away a very long time ago. But the people, the experiences and the impacts are all still there.