Alarm man we will have to agree to disagree as the old BS4737 states that a battry should be changed when it gets to 80% efficancy and the manufacturer tells you this happens when the battery is 5 years old and at 20-22oC if the temp is higher then the shorter the life. As I said the majority of calls I get both from joe public and the letting agent I do work for is " We had a power cut and the alarm went off all on its own and I could not enter the code to silence it" also when the powe does come back on they get into a panic put the wrong code in then lock out the panel. Another thing I have noticed is joe public will not get their system serviced so any wonder why they have problems