Image folder takes too long to do anything

Registration date
Sunday October 2, 2016
Last seen
October 2, 2016

I like to take pictures with my camera and of course save some interesting pictures I see on the net. I have them all sorted out into folders, but even then each folder would at least have 1000 pictures. The problem is every time I view or save a picture in one of these folders it takes at least a minute for it to finish.

The folder is optimized to picture format so my question is why does it take so long to do anything in my picture folder? I understand the first time might take long but doesn't Windows make a thumbnail file that caches the pictures for faster processing (I see this file when I disk cleanup)? So shouldn't it theoretically do all my processes fast?