How long is a piece of string?
The Achilles heal of most electronics is the electrolytic capacitors – if operated continuously at maximum voltage and temperature they will not last much longer than a year. A colleague of mine was a dab hand at repairing electronic equipment without a circuit diagram or much in the way of instruments. He would simply measure the in-circuit capacitance of the capacitors to find those that had died and replace them.
More often than not this would fix the equipment.
DVD/CD drives have the added problem of the laser diode lens which eventually turns opaque, rendering the drive useless, plus other moving parts that are prone to wear & tear.
Given the above – if a DVD or CD drive was used in shop continuously during the shop’s open hours, I would not expect it to last much more than a year (if that).
Although must admit I still have my first Sony CD player purchased around 1985 – but it does not get much use these days.