If ya have an image file of the game you want to back up saved on your hard disk then you can use that image file to burn as many disks as you like until you erase it . You can even send that file over the internet to another computer that you want to burn that backup on . Read the help files in the burning software you have and it will explain all this and more
Don't waste your time with cheap media , I learn't the hard way
and found it's definately worth spending a bit more cash for quality backups .