I have an old Plextor 4/12 that is still running, except the Win95 computer it is on, I just recently retired because I think it has motherboard issues, or something that serious. I think it is the number of burns, ...not nec the age of a CD burner that contribute more to its lifespan. I estimate I have made over 3000 copies on that Plextor.
These new "generic" burners, I might give them a couple of years. I got my Plextor in 96...I think...maybe 98.