There is never a reason why you shouldn't be continually backing up your data.
You never know when your hard drive is going to fail on you and I was the lucky pick of the draw yesterday.
This was the second 120GB Maxtor drive to die in recent years, so I decided to purchase an Western Digital 160GB Caviar SE (WD1600JB-00R) for my new drive. I have another 160GB Caviar SE (WD1600JB-00DUA3) in my file server and haven't had any problems with it so I figured it was worth a shot.
Thanks to the recent backup of my entire /home partition, I was back on my feet within minutes of installing Arch Linux.