I don't have CR2008, but I am guessing that they will export to an existing file, they will just overwrite it.
I don't think that Excel will export to an existing file and APPEND to it, it will overwrite it as well. Notepad is no smarter, it will overwrite, unless you modified the file inside of the app, same for Excel...same for 99% of all programs that will open a file and save it to another. (I leave 1% just in case)
Try it and see, I've been wrong before...