Lightroom slowdown - purge the cache

What do you do when lightroom begins to slow down a little? I had this problem around the new year. I'd optimised the catalogue and was at the point of splitting the catalogue into sections; keep the landscape stuff separate from the portrait stuff from the family stuff. Then I came across the option to purge the cache in the preferences.

When I did that, the whole lightroom interface speeded up by quite a lot, so I can only think that others will have had the same issue and that means me making a post about it to show how I did it and hopefully help someone out.

Step by step guide:

Hit Ctrl-, (hold donw the control key and press the comma) or Cmd-, on mac to get the preferences dialogue box up. This can also be found on the edit menu on windows or the lightroom menu on mac.
Click the tab labelled "File Handling" 

Then click the button labelled "Purge Cache"

Once this is done, a quick re-start of lightroom should have you back up and running. Note that you will have to rebuild the previews of previous imports as this will get rid of them - the previews, that is, not the images in the import.

You may notice in that last screenshot that I have a large cache set rather than the paltry 1.0 GB which was the default. This ensures that I don't have too many issues with LR having to rebuild previews if I go back a couple of shoots. The default 1.0GB holds a lot of previews, but it soon fills up when you're using a 5DII.

Hope this helps someone out at some point :)