I was awakened by the dulcet chirping of a smoke detector, gently warning me that the battery needed replacing. This occurs every 6 months (approximately) at 4 a.m. (precisely).
You need to buy higher quality batteries. ;-)
Our always goes off after DH heads to work, so I have to go pull it off the ceiling myself. I made him change them this last time...if I make him do it when we change the clocks it saves me all that grief.