Sounds like you are trying to copy (archive) some files important to you, to offline media. Usually with CD/DVD/Blu-Ray writers there will be software to split copies across multiple volumes, but that does not mean the computer you have ten years from now will be able to do restores; I've just been through that exercise with some copies made using Roxio tools.
One of the issues I had during restoration was how to deal with multiple copies of the same thing. During the period in question, I was saving data every month to every several months, so I might have 20-30 copies of some files over the life of a particular computer, and most had been transferred from computer to computer: desktop before going overseas, laptop overseas, desktop overseas, laptop on coming home, each computer successively larger storage capacity (usually by one or two orders of magnitude) than the previous. What really saved me on restore from CD and DVD was that the computer I was restoring to had 15X the storage of the largest disk drive I had archived.
Yes, if you are using appropriate software, you will be prompted for a new disk, when you do multi-volume copies. To CDs? The computer I am using just now would need at least 300,000 CD-Rs, 3,000 DVD-R or DVD+R, to back up just one full disk drive.
I am currently copying what is important to me to multiple external hard disk drives, much less expensive than removable media like CD-R or DVD-R.
Back up the total computer? A backup is quite a bit different from an archive, as it is trying to capture the state of a running computer, rather than saving or making copies of important files.
Few systems are actually capable of this, as things change during the backup. I've had more success with backups on Unix, VMS, and pre-Windows DOS computers than with Windows computers.
The Microsoft-provided Windows Backup Tool will back up "user files" and "data" Windows can also create a "system restore" (usually to multiple DVDs) that can get the OS back to a specific point, though you would likely need to re-install all application software, and then restore your user and data files. There are many third party tools that do better, and some (often provided with external hard drives and CD/DVD writers) that do not do as well.
There are third party tools that can make a mirror image copy of a system disk to a second disk. I've not tried this approach, as the state of my system changes second to second, I would maybe be doing nothing except making mirror images?
Figure out just what your goals are. If what you want to do is save particular files important to you, the best approach is often to attach an external hard disk drive of adequate size, and do a drag-and-drop copy. When your data volume gets beyond about 10 GB (50 CD-Rs) CDs become uneconomic (and they are not reliable long-term). For DVD-R, that cross-over is now about 100-200 GB, on media costs alone, not including your time.