The smoke detectors in my house have a nice feature:
They are hardwired using a battery as backup. When the battery gets weak they’ll start beeping. If the battery is removed at this point they will stop beeping. Best feature ever, IMO, as they always start beeping at 2AM and I rarely have spare 9V batteries on hand.
We change ours with daylight saving every year, it is a government run campaign and so I have never had batteries go flat on me. Change the time, change the batteries.
So I guess the whole “Check your alarm once a week” campaign used when I was in school didn’t work that well.
Also, while the temperature in my house goes down at night, that’s because the central heating barely works. With normal heating, I thought the temperature was supposed to be fairly constant. So I question this as a reason that smoke detectors mostly fail at night.