A little know fact about cd and dvd duplication is that when a duplicator burns copies of your disc, they normally do not verify that the data has been properly burned onto the disc.
The normal procedure is to check that the master disc or data is correct, then the data is burned onto the disc. For most applications this usually suffices, as the dropout rate for poorly burned discs is usually less than 1/10 of a percent. As long as your duplicator uses good blank media, your project should be trouble free.
However, for software or data critical discs, the need for a much higher degree of accuracy is required. For these applications and clients we typically run a verify on every disc. What does this mean? When we run a verify on every disc, our equipment is set to record the master data, then write the data to the disc. Normally this is the end of the process, however, for a verify, our equipment keeps an image of the data being burned on a hard drive, then instructs the burners to read the data that has just been burned on the disc. It then does a low level bit for bit comparison of every disc sector against the hard drive data image to ensure that the data has been accurately burned onto the disc.
For clients who need 100% confidence that their delivered discs will be accurate, this data verify process is unbeatable. Always keep in mind that burned discs use an organic dye to store the data and that it will degrade in time. So if your duplicator uses cheap discs that are out of spec, the initial burn may be ok, but 6 months or a year later, the dye can degrade to the point of making the data unreadable. So make sure your duplicator can provide evidence that they are using high quality blanks along with there data verification process.