Yes you can add more data later to a CD-R, as long as you don't finalize the
disk. I have found that other computers may not be able to read from an
unfinalized disk, or if you change the disk label when writing a new session,
the previous session may no longer be readable. These are good reasons not to
do this, but if you don't change the label between sessions and only use that
disk on the computer that made it, you CAN do this.
