How can I Fix My Panasonic DVD Recorder?

I would like to know how to fix my Panasonic DVD Recorder.
The problem is that when I try to record a movie, when the DVD is being updated (not finalized) after the recording, a note pops up that says " There might be something wrong with the disk. Press enter & self check will start." I do that & try to record again but the same thing happens. I've tried numerous DVD's & still the same. Also approximately how many DVD's can you record (life span).