A year ago I had trouble making coffee because my brewing scales refused to work. They run on two AAA batteries and even though it felt I had only just changed the batteries, it still felt like the quickest thing to test. Thankfully, with a fresh set of batteries I could get my coffee.
The question remained, how quickly do the scales drain the batteries? Since I didn't want to keep a spreadsheet, I took one of the small 2cm*5cm sticky note flags, wrote the date on it, and wrapped it around one of the batteries.
Today, I again had trouble making coffee. The small note said it was exactly one year to the day since the last battery change, so I could be sure that the batteries were the problem and that they drain at a reasonable rate.