Most light commercial systems are built to last 15 to 20 years. However, there are a number of conditions that can shorten this life expectancy. When outdoor and rooftop units are exposed to smog and salt air, as they are in NYC, corrosion and buildup of debris can cause damage to parts. The same goes for exposure to corrosive chemicals as often happens in manufacturing plants.
Neglect is probably the most common cause of an air conditioner’s early demise. Your system needs to be regularly maintained in order to get the maximum life expectancy. That means having it serviced once or twice per year (ideally, once before start-up in the spring and once after system shut-down in the fall).