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).
Im having problems with my OPTIARC DVD RW AD-5680H writer and my imac is exactly 2 years old so out of warranty! I don't think I use it that much so a little disappointed that its starting to fail after what I think is a short life. Ive ended up buying a USB external for just £12 and it works well. It will be interesting to see the life span!
the lifetime is a statistical number
it's called mtbf
samsung would have the mtbf number of the drive
but you can't really use it for anything more then you would be able to use
the statistic of how often people with the same first name as you won the lottery
all companys will aim at keeping the mtbf longer then their warrenty because otherwise they will lose money
so if your devices fail within warrenty you're lukcy you get a new one
if outside you have to buy a new one
if you're dissapointed in the lifespan of the drive then more expensive models maybe from other brands would have a longer MTBF