FYI,
After rebuilding all thumbnails I have gone from 1GB+ down to 474MB.
I have navigated through all View Schemes building various sizes, media types, and using all various viewing criteria (e.g. Artist, Album, Album Artist (Custom), Genre etc.)
Doubtless, the thumb cache will get bigger but I'm curious why it has almost doubled in size to provide the same results. I watched this happen before and I like to minimize the size of this folder in order to more easily copy it over to my laptop as a backup on a regular basis.
DC