Yesterday while cooking I set off the smoke detector, no I did not burn anything. They go off when I cook over a high heat. And yesterday once they started going off they would not stop. I ended up having to disconnect them all (they are hard wired with an interconnect) and I replaced them this morning. Aaaaaaaand let me tell you, I had a sleepless night last night knowing there were no detectors installed.
https://www.southernliving.com/how-often-should-you-replace-smoke-detectors-8774122
This is anecdotical but I moved into an apartment with a 30 year old ionizing smoke detector, and the failure was it was too sensitive, I assume because there were less electrons being emitted from the radioactive element, any faint smoke caused it to go off. Eventually it got into a state where it would always be in an alert state, and was beeping 100% of the time, which was when the landlord finally replaced it.
My assumption with the 10 year replacement recommendation for Americium based smoke detectors is to replace it before it becomes too sensitive and annoying, because they were worried some people would remove the battery and just live without an active smoke detector.
There’s no radiation drop after just 30 years from americium 241. It has a 450 year half life. After decades electric components start to fail and\or things get dirty. After 30 years of getting smoke in it, there was probably a layer of dust\smoke over where the radiation is at that were blocking some of the radiation all the time, that made it more sensitive.
Same issues will happen with photoelectric detectors. It’s recommended to replace both types after no longer than 10 years. I have no idea where the person you responded to got the information about them not needing replaced as often as ionization detectors. If anything, it’s actually the opposite.