Robert,
As much as you might think that your pictures are taken, "without a thought", remember, 9/10ths of our brain processing in preparation for a picture is not something we are aware of, but below our consciousness radar.
A person who has composed myriads of shots in a professional career, has developed fine automatic skills that call on memories, knowledge, esthetics, experience and eye, brain motor coordination, so what would take a good enthusiast 20 seconds, you can accomplish without any apparent effort in a fraction of a second!
You have a large resource of worthy works of art to mine.
And yes, 200,000 is a vast number to go through! So get a curator volunteer, perhaps!
Asher