Since I converted to Nest six years ago, I have had zero false alarms. I had gotten tired of false trips on First Alert from humidity (among other causes).

I only test mine about twice a year, I like that they report their status to the app, so I can check battery level.

My house is old, I have battery only units, no hardwire. Having the units interconnected over radio was critical for me. I installed with Duracell Lithium batteries, and have not had to change them yet. I wonder if they’ll go the full ten years on one set.

They are expensive, I will grant that. Also note that they use a photoelectric smoke sensor, which is great for smoky smouldering fires, but slower than ionization based detectors on fast burning fires.

You don’t have access to ebay?

I have bought three old Optiplexes, similarly equipped, each under $100.

They are great as dedicated servers.