I am doing a report on some defects and one includes an alleged defective control panel . What would be the life expectancy of a panel would this be 5 years or more if maintained properly. If not maintained would this be less than 3.5 years.

Are you sure you are not meaning the battery in the fire alarm panel? Fire alarm panels should work for 20+ years, if well maintained. (I have seen panels that are older than this still working) But the batteries in the fire alarm panels should be changed as and when required which is usually a 5 year maximum.