Smoke detectors are life saving-ly important, BUT.
Whoever designed them so that they start chirping and beeping at 4 am because the battery is running down needs to have a serious talking to.
In fact in the past 5 years I only remember a smoke alarm chirping once during the day.
Why do they always chirp at night? We will find you and give you a new battery, but please ask during the day. ☺