I've thought about making DVD backups, although with the size of a DVD, it would take a while, even for the essentials, plus you have to split it all to fit. And then you still have to worry about how durable they are.
Redundancy is always good though. The more backups you have, the less chance of losing data. My externals have saved me a couple of times. First, when my 500GB drive died (which had all of my TV shows and movies on it), then when my 320GB drive started failing, I was able to back it up and migrate over to a new drive much easier. I've luckily never lost any notable data in the entire time I've had my own computer. I still have backups of my floppies from my old 486!
I'm most worried about the irreplaceable than just mere pain in the ass to replace. If I lose TV shows, or music, those files exist elsewhere, so I could replace them, even though it would be a hassle. But then I have all of my own work, that doesn't exist anywhere but on my PC. I don't know what I'd do if I lost any of that.