Most smoke detectors have a 10 year warranty. In addition, the ability of a smoke detector to function reliably after 10 years of service is diminished. We recommend that smoke detectors are replaced AT LEAST every 10 years.
However if they are not cared for they tend to have a shorter lifespan. We recommend that you gently and carefully vacuum smoke detectors from the outside (don't take them down or apart) once per month to keep dust, pollen, pet hair & dander, etc. out of the detector.
If your smoke detector starts beeping and it's not due to a low battery, or it does not have a battery backup, it's time to replace it.