Quetion about Time Machine as backup for college student

[deckeda]

Disc Utility can make backups of the install discs. The gist of it is to put the one in you wish to copy, wait for it to mount, launch Disc Utility and at the File menu choose "New Image from (name of disc)" and choose Master DVD or whatever from the little popup list later. That's what makes the resulting image bootable.

You'll get a disc image file on your desktop, eject the install disc and pop in a blank (dual-layer) and use Disc Utility to burn the image sitting on your desktop by selecting the disc image now shown in Disc Utility's left-hand side source pane. Easier than I make it sound.