I just noticed there are 2186 thumbnails in my uploads folder created by Video Thumbnails. This on a site with approximately 50 videos. It seems that every time I make VT to retrieve new thumbnails by either resetting the thumbnail on the edit post page or scanning all past posts in the VT options page, nothing happens to the old ones. 2186 files for 50 posts is an exception, since I had been testing a lot while making updates to the plugin, but every user suffers from the same problem to a lesser degree.
Should we either delete the old one when retrieving a new thumbnail, or keep and use the old one instead if the thumbs are exactly one and the same? This could easily be checked for example by comparing the md5 checksums of the existing file and the new not-yet-written-to-file string.