I have a Windows Server 2008 with Volume Shadow Copies active on a drive D:\. I gave the vss copies a quota of 30 GB. Usually it allowed me to restore the files back for about 3 weeks.
But then a strange thing happend. Now almost every week all the vss copies get lost in the history and there are only 1-2 days back in history. I think there is only the history lost because the amount of uses vss disk space remains the same.