In my mind, if everything is working fine for you, do not upgrade. You will get some software not found on the FTP, but since you aren't asking "why is this not working" questions, I wouldn't sweat it.
In my expereince, SUSE has a habit of breaking when upgrading. If you do want to use the new disks for an install, do a new install with a fresh format first. Otherwise the disks have lots of packages on them, you probably do not need to go to the internet to get RPMS.