mundane - fire detector batteries replaced

replaced all 4 batteries at the same time is,
1 from old pack,
3 from new pack
final replacement on 2016 08 24 noon

how long do these last? HAHAHAHA
down stairs, bedroom and hall are on AC and battery
office is on battery only, but there are WIRES, SO I could AC connect the FD
too many wires, so I gave up

revisit soon ?? hahahaha  FML