We live in WA state, and the county (or state) requirement is that fire alarms have to be hard-wired with battery backup if your house is newer than a certain age. The ceiling in our great room is almost 20 ft. tall. When we had ceiling fans installed, I begged my husband to have that particular fire alarm lowered so that it would be in a more reachable area, but he didn't want to have it moved. Therefore, when the battery goes out, we have to use a Genie lift to get to it because of the location. We can't lean a ladder against a wall to get to it. Hence, last time the battery went out, we replaced it with a 10-year battery. Hopefully it will last that long! My husband is Mr. Preventive Maintenance, so he makes sure all of our batteries are in and working. With the alarms being hard-wired, we have to keep working batteries in them or they will continue alarming until the battery is replaced.