Heat detectors are designed to respond to a fire, but not smoke. Using heat detectors instead of smoke detectors should help reduce false alarms from things like cooking. The Lifespan of Smoke and Carbon Monoxide Detectors. Most smoke alarms have a life span between eight and 10 years, and again, replace the batteries every year. A smoke detector with a titanium battery or a hard-wired smoke detector can last 10 years, at which time you would just replace the whole unit. Carbon monoxide detectors last between five and seven years.