All of my email accounts are IMAP accounts so I have my email anywhere I go. I always worry about making a mistake and losing all my emails. I found this great program that lets you backup your IMAP emails and folders.
http://www.broobles.com/imapsize
To schedule a backup:
imapsize -backup -account=test_account
Hello
I use Thunderbird and Gmail.
If google looses anything i still have it in my thunderbird. If i lose it in my thunder bird i still have it in my gmail. I do believe that it is always good to back things up. But this just saves me time and trouble and hard drive space.