There is nothing more annoying than having the battery on a smoke alarm go south at 6:40 AM on Saturday. (Unless maybe at 3:00 AM on a work day.) Beep. Wait one minute. Beep. And on and on.
Usually my better half takes care of this stuff for me, but he’s backpacking this weekend, so it was up to me – get up, get the ladder (from the basement), climb 2 flights of stairs back up, take down the alarm, replace the battery, put the alarm back up. By this time, of course, it was about the time I was thinking about getting up anyway; but I refused to dictated to by a device. I went back to bed. For 20 minutes.
Fortunately we had one (count it) good 9V battery in the house. Add that to the shopping list.