If incd and packet writing is NOT worth the trouble

how do i back up multiple small files continously??? multisession wastes a lot of space to set up a session i gather.

If i use a RW disc, would the old data be written over, or is it masked and new session rewritten again??

Multisession wastes a lot of space on CD-R and on DVD-R/RW, but not so much on DVD+R/RW. So you could use a DVD+R/RW and multi-session (wasting 2MB per extra session).

You could also use two discs with InCD (or other packet writing application) and back up the same files to both of them. In that way you minimize the risk of losing all the contents on your backup disc if something goes wrong with packet writing.

Then when you have filled up your re-writable disc, you can copy the contents to a recordable DVD+R or DVD-R disc for long-term backup.

That depends entirely on how you do it in your burning application. It can be either of those options you describe. It can also be a third option - the old data is still there and the new data is just added in the next session.