All my stuff is on EHD and I also burn to DVD. I have folders on my EHD for each designer and my photos are all by month.
Then, I have a folder of "To Be Burned to DVD" where all new kits go after I've used them. When it's got 4GB, I burn to DVD. The only problem is? If I ever need to find a kit, I won't know where to look unless I have an idea of when that kit was released or when I used it.
So, not the best system, but at least it IS backed up. I guess I need to have a printed list of what is on each DVD. That would help.