RezQue guyz
Changing batteries twice a year came out when carbon zinc was the standard cell, probably why Mike remembers it so well.
Even the cheap batteries supplied with smoke detectors bought today are good for at least a year.
Once a year is good as long as you change them once a year. Use new quality batteries (i would stick with name brand) and if you want to minimize your change outs you can now buy 10 year lithium batteries. Some detectors even come with the 10 year batteries now, Including the newest CO detectors (you all do have a least one CO detector - right)
And if you really want to try some hi tech, you can now buy batteries for smokes that have a microphone and WiFi capability (5 year change out).