Updating thumbnails in iphoto
Of course, what I call Snapshot would be an expert file saved with the folder - but not a cache as it is now.
More like a high res photo file of the folder contents.
Apple’s latest app Photos is now available for free as part of OS X 10.10.3 for Mac.
Thumbnail Annihilator is included in the Duplicate Annihilator package that you can download from this site.
Bridge already has 3 ways to speed up the thumbnail embedding and reading - but it's still painfully slow in folders of hundreds of files for ex.
There should be a 4th way of thumbs handling - found in some Slideshow viewers It should read just once the content of a folder and take a "Snapshot" of the thumbs as found at that moment.
Though it may appear in the Finder that both libraries are taking up the same storage capacity, only one library — your Photos library — has the majority of the data.
Apple has a support article written about this under-the-hood magic if you want more information, but the short answer is: If you don't want to use i Photo or Aperture anymore, feel free to delete your original library. There's a setting you can uncheck to just link to your photos in their existing locations, rather than directly importing/duplicating them.
Then will only add more thumbs if it's asked to Update. Especially for Archived folders - that don't change their contents for years - it would be a blessing.