good answers ....
but in reality ... every time you add a session (max of 4?)
the whole cdfs is replaced .... 20-40 MB
and every time you do it you risk bugg*ring up the disc.
just because you can doesn't mean you should .... at least not where backups are concerned. it's ok compiling a music CD ... or with dvd filling one with your recorder ...
but for backups ... it's dodgy because if it fails you don't just loose that days backup.
at 20p for a decent quality disc .... it's safer to splash out
not so many these days ... but I've made my fair share of coasters burning CDs