The End of Life for the detectors we are most familiar with (Smoke Detectors) comes in two ways generally. Either they get locked into a continuous state of alarm because they are dirty or, as in the case of all residential Smoke Alarms the code says 10 years and out. System Smoke Detectors are tested at least once a year and can last 20 or more years with proper maintenance.
Carbon Monoxide (CO) Detectors and Ultraviolet/Infrared (UV/IR) Detectors do not have the same chance at longevity. The life expectancy of either of these devices is generally 5 - 7 years.