Hi! I know very little about smoke detectors and am looking for some advice. We have several Lifesaver Kidde #1275 detectors that are approx. 8 years old. They have started sounding their alarms at night, 2 or more at a time, for no apparent reason. We have never cleaned them, only replaced the batteries when they chirp. I read on one of these Q&A websites, that the useful life of a smoke detector is 8-10 years. Do we simply need to replace all of our detectors or is there something else we should try first? Thanks in advance for any advice/wisdom on this subject! Christina