They replace the battery when it starts beeping. I replace the battery when it starts beeping. It's kind of a waste to replace a battery yearly when the backup batteries only die every three to five years. Replacing them yearly is also a way to put a lot of additional hazardous waste into landfills, given that a lot of people think that correctly recycling consumer batteries is bs.And if you would just replace the batteries every year, they would never go off except when you needed them to.
Your the reason we keep hearing this pita psa.
The PITA PSA is mainly due to slumlord type landlords who disconnect and disable smoke detectors in apartments even though they're required to keep them functional. That's the typical place where you find disabled smoke detectors. My dad used to do apartment inspections and something like 50% of properties failed because the smoke detectors had been intentionally disabled so they didn't have to be "maintained" (by putting in new batteries on a regular basis). I always tested my smoke detectors after I moved into an apartment and complained until it was made functional. I think I only ever moved into one apartment where the detectors were functional off the bat.