I think most of us made ISO copies of all our software a long time ago. I have images of 8.5 spread across probably 6 hard drives, most are sitting on shelves now. I don't keep anything on burned disk. Disks can get scratched and a burned disk is actually light sensitive and has a limited shelf life. The original disks will be pressed so if stored properly could last forever, but a ISO copy is easier to use.
I now have a 1 TB external drive dedicated to nothing but software. It has Sonar going back to Guitar Studio and then 6 and 7 and so on. Wave lab 4, Nero 3 all sorts of stuff that probably won't run anything but XP, but I keep it anyhow.