Smoke/ CO Detector

So the smoke detector in the unfinished side of the basement started chirping, and that got me looking at the rest of the smoke detectors. They say the lifespan of these things is five or six years, but who thinks of them that often? looking at the date of the "master" one above, it is clear that it is expired one way or another. So, off to Home Depot to buy three more (they are all chained together somehow) at $60 each. At least these ones "claim" to have a ten year life span, so I've put a big label on the front of them with the May 2026 replace-by date on them so we are less likely to forget.