I need to purchase at least a dozen 1.5 and 3 volt batteries for a home security system. The system manufacturer suggests we purchase the replacement batteries from him, at about $8.50 ea., because of the long life afforded. I have decided to purchase the batteries at a local store. My question is, how much better, in terms of life expectancy, is the best battery offered compared to a lithium battery?

Lithium batteries will last longer than any other battery types, including alkaline and zinc carbon (lowest cost) batteries, in most high drain devices. For example, RAYOVAC®'s 9-volt lithium battery will last for 10 years in an ionization-type smoke alarm (the most common type), compared to about 3 to 5 years for an alkaline battery and just 1 year for a zinc carbon battery. In a photoelectric smoke alarm the lithium battery will last anywhere from 3 to 7 years vs. about a year for alkaline. Depending on the specific device, the same approximate ratio holds true for other security devices such as door/window transmitters, infrared motion detectors and glass break detectors. It is generally a good idea to follow the manufacturer's battery recommendations.