What to do with purchased music

[dreamshark]

For all the time I spend with iTunes I haven't bought that much music, but I have bought some. 8 albums and about the same number of individual songs. I know I should make some kind of backup copies, but what? I could burn them to CD, of course, but I don't really want more hand-labeled CDs lying around. If anything, I'd like to start getting rid of the CDs that I have digitized. This would be a perfect use for DVD, but I don't have a DVD burner in my increasingly aged computer. I do have all my music backed up on an external hard drive, but since it's turned on and plugged into the computer all the time that isn't a lot of protection against something like a lightning strike. Maybe a thumb drive would be a good solution.

What do other people do to back up music purchased online?