hi...i have an iomega 12x10x32 cd-rw. what confuses me is...i thought CD-R disks could not be written-to after used once. but i found that, at least with this one fild i keep modifying, i can save it over and over again on the same CD-R disk. why is this? how is it that i can continue to write to the cd-r? will this last indefinitely?