Today, I changed the batteries in all my smoke detectors. I noticed that the battery light in one was blinking. Instead of only replacing the one with a new normal 9v battery, I ordered a pack of 10-year lithium 9v batteries and replaced them all. Now I don’t have to worry about changing them for a handful of years.
Edit - Funnily enough, dinner put them to the test. I was going to test them tomorrow when the kiddo is at daycare.
No, smoke detectors have expiration dates. The device itself is supposed to be fully replaced every 10 ish years (it varies by model). Over the years the sensors degrade and stop working as well.
https://www.defense.gov/News/News-Stories/Article/Article/972455/every-smoke-alarm-has-an-expiration-date-whats-yours/
Models with non-replaceable batteries designed for the device’s entire 10 year lifespan generally work out to be the best option these days.
“New battery day” simply gets replaced by “new smoke detector day”.