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
The half life for americium 241 is like 450 years. The 10 year replacement has nothing to do with decay. It’s just a non specific safety in case any of the electronics or board etc start to fail. Photoelectric detectors have the same 10 year recommendation as a max.
It’s actually recommend by many organizations (like the NFPA) to replace photoelectric detectors more often than ionization detectors, if anything.
It’s tuned to a specific output and isn’t exactly field adjustable. Certainly it will continue to be radioactive long after you’re dead, but that doesn’t mean it will still be working properly.
I know exactly how they work. I’m a firefighter and a hazmat technician. Plus I work on and repair electronics as a hobby. Your smoke detector failing after 10 or 30 years has zero to do with radioactive decay. It’s from contamination (dust) and sensor degradation. Once the metal plates inside get enough buildup from dust (like smoke dust and regular dust) and contamination from humidity, the charge that’s supposed to be detected between those plates from the ionization stays lower all the time. That means less actual “smoke” is needed to drop it below the threshold. This happens MUCH faster than radioactive decay reducing what it will ionize.