How long can you continuously burn for?

I burn a lot of CD/DVD’s in sucession and always wondered what was the safe time limit you should stop and let your CD-ROM cool down before continuing to burn again. Is it like an airplane engine which works better if you keep it running constantly or should you say burn 30 CDs and then let it sit idle for awhile and then burn again? I have a fan over my CD-ROM to keep it cool but I’ve always wondered if I was pushing my CD-ROM too far or if I was watching my CD-ROM rest idle to cool down when it wasn’t necessary. Anyone can shed some light on this? I did happen to burn a lot of CDs on my Optorite in one sitting once and then the servo kind of busted and could no longer burn DVDs due to its size. I had thought it might have been caused by burning too many CDs in succession but of course its hard to tell.