The end of the writable layer can be of poorer quality than the rest of the disc, which means that read errors can occur at the end of the disc or in areas outside the normal storage area of the disc. In the case of audio CDs this means unexplained errors, all types of sound interference and the audio CD player hanging at the end of the CD. For data CDs it means that it is not possible to read a number of files.
The burning process may be interrupted near the end by an error message, such as 'Write emergency' or 'Track following error'. However, the CDs can often be read almost up to the end, despite these error messages. The point on the disc at which errors may occur is dependent on the make of the blank disc and the type of recorder. As there is no way of telling the exact excess capacity of a CD automatically, you will unfortunately need to make a few experiments.
The third and most unpleasant problem is the possibility of damaging the recorder. In practice this is unlikely to happen.