We think of CD's and spinning magnetic disks as standards but they'll be obsolete soon enough, just like the analog tape and Syquest and Jaz disks we used to rely on.
Ummm, maybe YOU think of CD's as spinning magnetic disks, but I think most folks would think of them as spinning optical discs. They do not record information magnetically like analog tape or Syquest or Jaz discs. They DO have a potential to eventually fail, especially cheaply made media like that sold at Office MaxDepotWarehouseMegaoutlet Inc. I've never had one fail yet in over ten years of using them to backup data, but allegedly they will.
I agree with the redundant backup strategy you mention. Have two drives that either mirror each other in a RAID configurations (there are plenty of very reasonably priced 2-slot RAID solutions out there that are easy to swop drives into), or do a weekly swop of two separate drives that mirror your original.
It is not a question of IF your hard drive will fail, it is simply a matter of when.