Instead of worrying about making a duplicate of your OS X install disk (because the OS gets updated you wind up getting the newer version disks anyway) why don't you consider
cloning your perfect boot configuration to a external drive?
This way you get everything, all your iTunes tweaks, iPhoto's, software updates, program installs (even copy protected ones, some require re-registering) and everything on your boot drive. You can even boot from it and grab your files from a funky OS and reverse clone.
The OSX install disk should very rarely have to come out of it's protective package this way so it will be preserved for a real emergency.
To learn how to clone your boot drive with maximum reliability read my text documents on it
http://homepage.mac.com/hogfish