Your average home smoke alarm will last for a long time, with frequent battery changes and cleaning... however... there is a standard for them. They are to be replaced every 10 years in normal home conditions. And with the costs of them dropping every year, its not a major issue to replace them as it was years ago when smoke alarms were fairly pricey.
But still, i go to calls and there are places with no smoke alarms at all, or they arent working... i just dont get it...
All men are created equal, a few become fire fighters.