Also note that there can be substantial variability in the test results obtained from commercial testing equipment, so your media testing should always be done on the same piece of CD test equipment. The measured results will be relative, not absolute. Periodic verification of your recordings helps you maintain an appropriate quality level. If you never verify the data, then sooner or later you will have a problem. An absolute zero defect disc is not possible.
All discs have errors.
You should verify the data and learn how to use a CD quality analysis tool to determine that the quality of the recording is within the specification limits for errors. The finalization process is the last part of the multisession recording process which writes the overall disc table of contents into the disc lead-in area, making the disc conform to the ISO 9660 standard required by most reader and reader driver software. My CD replicator tells me their analyzers show that my CD-R master discs have errors, but before I send the plant any disc, I play them on a variety of CD players and never notice a problem. Please refer to the Resources Listing for vendors that specialize in making these measurements. One plant rejected my CD-R master disc because their analyzer reported errors.