Many people buy cheap. no brand dollar store batteries that have a much shorter life than the name brands. So, twice a year when you change the clocks, you also change the batteries to help protect your family and guests.
We have hardwired smoke alarms which don’t need battery changes, but because we live in New England where winter storm power outages occur, we also have battery operated alarms in the bedroom areas. I don’t spend $4 each for Duracell 9V batteries for these when because one doesn’t need alkaline batteries for this type of use. I buy Sunbeam at Dollar Tree 2/$1. Last night I changed the 7 alarms.
ALWAYS mark the installation date on the battery with a Sharpie. Years ago I had an insurance company try to cut the amount of a claim stating there was contributory negligence because I did not have a ‘good’ battery in the smoke alarm. The battery had dating only 4 moths old. The CT Dept. of Consumer Protection found this carrier was using this excuse regularly and many people just accepted the lower payouts.
In fact, our local Volunteer Fire Department will come and change batteries for the elderly or disabled at no charge.