I came up with the idea about 3 years ago, back when I didn’t know anything about flashlight forums.
I got pretty excited when I saw the Uber thrower thread with people that had the same idea as me 
Unfortunately it has already been patented, but I guess that means I don’t need to worry about people stealing my design…or pay fees every year.
Until now I’ve been sticking to lenses because I thought they were better, but I’m kinda hitting a wall, and the chromatic aberration I discovered in this thread makes me not like lenses as much anymore.
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Yes, most of the airflow goes through the collar.
Thanks to the mesh at the back of the flashlight I don’t have to worry about large particles or insects getting inside the light or on the collar.
Some dust does settle, but very little since it is a very smooth surface and almost nothing sticks to it, the air just pushes right past.
Not really worried about it oxidizing, cold mirror coatings are pretty resistant to oxygen environments.
The reason I wanted lots of air flowing past the collar is to keep it from fogging up in high humidity environments, and water on it would almost certainly damage the coating.