There is an issue in runTrimRecentChanges() that results in changelog file being updated much too often. It's Windows-specific (I think) and is related to the changelog creation time check. Because of the file system tunneling [1] the creation date is never updated and the trimmer always thinks that the changelog is too old.
[1]
http://blogs.msdn.com/oldnewthing/archive/2005/07/15/439261.aspx