The longer they are, the longer it takes a server to dig them out and send them down to the requesting browser. That's still too long, but a significant improvement. If you have played around with themes in a web, either adding or changing themes or importing pages with themes on them, you are urged to flush all the themes from your web and re-apply them, in the later stages prior to publishing. Show documents in hidden directories'. Close all pages.
Open Folders View.
Your theme is gone. Close all pages. Open Folders View. From the scroll window select the desired theme. Check the appropriate Vivid Color, Active Graphics and Background Picture.