Most PCs provide little to no airflow to Optical drives and they work for the most part. You will still get in trouble if;
1. The drive is crowded with hot components with no room to breathe - HDDs for example.
2. The drive is used in a fashion that it is constantly running in full spin mode (ripping or writing)
Optical drives for the most part are fairly inddifernt to heat, but then again people on this forum are known to push the boundaries.