Optical media doesn't hold enough, though. I've got a terabyte of downloaded media. Even with Blu-rays that hold 50 GB, I'm not going to bother burning and storing and keeping 40 of them.

I go with simple external hard drives. I get a new one every couple years and copy everything to it as my main backup. The likelihood of my in-machine drive and fairly young backup drive failing at the same time is pretty low. Even if that happens, the previous backup drive will have a good portion of it. And my important docs folder also goes to Carbonite online backup.