Smoke Detectors

I know that we are supposed to change the batteries in the smoke detectors every time we change the clock for Day Light Savings.  We never do that.  Who has time to change the batteries twice a year when you have a smoke detector in every room of the house, while you are adjusting to the wonderful new time change you just received?  Besides that is a lot of money wasted on new batteries that you don't really need yet, especially when the smoke detector beeps to let you know that the batteries are dying.  That brings me to the point of my entry today.  Why is it that the smoke detector only beeps in the middle of the night to let you know that the batteries are dying?  Is that the only time it can give you this info?  Why not in the day time or the evening.  At least sometime when you don't have to crawl out of bed, realize you don't have the right size batteries, and then either endure the annoying beep all night or go to either Kroger or Walmart (don't get me started on that) because they are the only stores open at 3 am.  To the techno people out there, can you get with the people that make the smoke detectors beep to let you know the batteries are dying and try to figure out a way to make them beep some other time but the middle of the night?  Just wondering?