Google wants us all to keep everything floating in their cloud, but it's always a good idea to keep a backup of your email. Sure, it sounds impossible, but you never know whether Google will be around in ten years time. There are lots of ways to get your entire Gmail dump onto your desktop. We like Gmail Backup which is graphical for Windows and command line for Linux and Mac OS X. If you prefer a command line tool, check out Fetchmail or just use Outlook or Thunderbird to download them via POP access.