Yes, Smoke Alarms should be thrown away. The element that detects smoke has a 10-year maximum life span, which is exactly why most have moved to a non-replaceable battery that forces you to throw it away (for safety).
I'm going to need to see some data to back up that claim. Americium-241 has a half-life of 432.6 years. The detector itself isn't going to degrade in any meaningful way after only 10 years.
Plus, many smoke alarms these days use a photoelectric sensor which don't wear out but are prone to false alarms from dust, etc. Smoke alarms SHOULD be cleaned at least once a year, by blasting them with compressed air. Dust buildup is a very common reason that smoke alarms stop working as well after any number of years. They require regular cleaning, just like everything else in the house.
Non-replaceable battery smoke alarms are popular because they are much more convenient to own. And you should NOT throw them away, the batteries in these contain lithium and must be recycled.
Interesting. We bought a bunch (5 pack, 6 pack?) from Costco IIRC about 3-5 years ago, and they all take 2 AA batteries, which is great because we've doubled down on Eneloop batteries for everything possible..
I didn't have to look far to replace my combo CO/Smoke detector or do a ton of hard searching to find one that just took a 9-volt. The first two results on Amazon US for "smoke detector" take 9-volts.
Those exist and are still available but are fairly outdated in the US. The sealed lithium 10-year disposable is the newer standard. And, actually, building codes for last several year requires them to be hardwired so no batteries at all.
The landlord special on older construction (maybe >10 years old, can't remember when the hardwire code went into effect) will usually be the 9v. Because they don't care about you having to get on a ladder to change the battery every year. They get to save $5-10 per smoke detector. Practically any homeowner is going to choose the 10 year option as the batteries don't have to be swapped.