This is only true for the Americium based smoke detectors. The newer photoelectric cell fire detectors don’t decay like Americium detectors, and as long as you replace the battery it’ll be good for however long it’s internal components (capacitors and whatnot) will last.

Technology Connections has a good video about this subject:

https://youtu.be/DuAeaIcAXtg

This is plain WRONG and DANGEROUS.

The issue is NOT the Americum but the natural degration of the photoelectric cells and the accumulation of dirt within the test chamber.

Even before that time the risk for false alarms is increased substantially by degration before the chances for sucessful alarming decrease rapidly. Due to that they actually withstand aging actually worse than ionisation based devices.

Sientific sources?

Here

here.

Here

Here

(Besides: Americum has a decay time of over 400 years,btw)

Your third source is about the 2020 follow-up study of the 2017 study in your first source. You’ve “only” (in scare quotes because that’s still plenty) got three independent sources even though it looks like four.