Media shift

I've been working my way through the task of transferring all my saved data (mostly work and personal images) from optical media (CDs & DVDs) to hard drives.
With some time to kill in a cafe it was a good opportunity to copy over another wee stack of disks onto a portable drive before making a backup copy on a larger external drive. Some of my CDs are over 10 years old but I've only had a couple of very minor file corruptions.... now, do I throw out all the old disks, or keep them as extra backups...?