1) It's not that hard to take low doses of psychedelics as regularly or irregularly as you'd like. They are extremely non-compulsive.
2) Testing is not so hard these days in many parts of the world. In my city there are at least a couple mass spectrometry machines available for free testing. Besides that, no need for powders from the internet; growing magic mushrooms at home is a simple project anyone can take on.
3) No we don't have a study, so like a lot of things in life we have to rely on more informal observation and anecdotes. A couple of other notable psychedelic old-timers are Albert Hofmann, Paul Stamets. I've met many "psychedelic seniors" over the years, and they've always been very bright, admirable people.
Personally, I've been using psychedelics for 30y, and while I can see that they aren't completely without risks, on the whole they are of great benefit and I plan on aging into becoming one of these psychedelic seniors myself.
4) Psychedelic use is associated with improved mental health outcomes: - https://journals.plos.org/plosone/article?id=10.1371/journal... - https://journals.sagepub.com/doi/10.1177/0269881114565653 - https://akjournals.com/view/journals/2054/5/2/article-p83.xm...
I haven't heard of the psychedelic chemist who had a mental breakdown, I think that's a myth. The biggest risk to mental health for a psychedelic chemist is ending up in prison.