Don't know about samsung, but if you puruse the offerings on Amazon, NewEgg and such places, the average MTBF for an internal DVD burner seems to be anywhere from 50K to 100K hours. But MTBF is jus that, the average time to failure from a limited sample (limited in the number tested and in the duration of the test, since they usually use a short test at extreme settings to simulate long term use). There will be many units that fail at less (some at MUCH less time) and many units that go much longer.
There really is no way to determine a real meaningful lifetime for such devices - it depends entirely on how much they are used and under what conditions (do you live in a hot humid environment, is it used in a dusty environment, is the power supply used stable and consistent, etc). That's actually why it is often even hard to find published MTBF ratings for such components, since it's not a terribly informative number. I've had identical hard drives (same make and model, same 100K MTBF rating), used in the same RAID enclousure - some have failed within months (one within a couple of weeks), and others just keep going for years and years.
If this is a component you depend on for work/livelihood, just buy the best one you can afford. If it is truly critical and you cannot afford downtime, buy two, and keep one as an emergency spare (and then replace it immediately once you have need to use it).