This article is from the CD-Recordable FAQ, by Andy McFadden (firstname.lastname@example.org) with numerous contributions by others.
The MTBF (Mean Time Between Failures) on these drives is typically 50,000
to 100,000 hours, and they come with a 1 year warranty. Compare that to
hard drives rated at between 500,000 and 1,000,000 hours with a 3 or 5 year
warranty and that should give you some idea.
Most of the drives available today weren't meant for mass production of
CD-Rs. The only exceptions are the venerable Philips CDD 522, Kodak PCD 600,
and Sony CDW-900E.
Incidentally, MTBF is not an estimate of how long the drive will last.
Rather, it's an estimate of the failure rate of the drives during the
expected lifetime of the device. Once you exceed the expected lifetime,
which is often on the order of a couple of years, the anticipated failure
rate increases. If you have new drives with an MTBF of 25,000 hours, and
you run 1000 units for 100 hours, you can expect to see four of them fail.
It does NOT mean you can expect them to run for 2.8 years and then all fail