If you want to be really sure of maximal shelf life, you'd use glass instead of polycarbonate as well - the manufacturing technology exists: https://www.theabsolutesound.com/articles/the-2000-cd-made-f...

But all of that is really not relevant at all for backups because the CD-R dyes will degrade long before the reflective layer. The shelf life of the reflective layer is an issue when talking about pressed discs.