Sometimes Time Machine spends a very long time "Cleaning Up...", and I am curious what it is doing. There is also a button in the Time Machine menu, "Skip Cleaning Up". I have clicked it, and it seems that it does not damage the integrity and completeness of the backup that took place immediately before. What is the purpose of cleaning up? What are the consequences of skipping it? Why does it takes a really long time on seemingly random occasions? For instance, I just plugged into my Time Machine drive for the first time in several hours. I had run a backup maybe 4 hours prior. When it was "Backing Up", it said it had 109.6 MB total to backup. It did that in about 2 minutes. Now it has been "Cleaning Up..." for at least 20 minutes. It is still cleaning up as I type this.