You forgot to mention titanium and plastic as regulator materials. Real and synthetic rubber if you want to get more inclusive. Does anyone besides Atomic use stainless steel for first stages?
When I lived in Point back in the 70s I was in the inlet most nights between June and October when the tides were right, mostly at night with my big yellow Allen Light. I did some wreck diving back then, but have cut back as I've gotten older and less tolerant of thermoclines and idiots. Still, I was diving off Barnegat inlet last week.
Being retired allows me to do all my diving mid-week. I also do three or four Caribbean trips each year, and I service my own equipment.
WD40 is bad news, especially when used around scuba equipment. I'm amazed that anyone would spray a volatile petroleum distillate in any part of a regulator. The stuff is poison, and it can weaken or dissolve rubber. I mentioned guns only because I know the hatred for WD40 is so acute in that community.