Durable and low

Since I am responsible for several homes, I was sorry to be summoned regularly to beeping smoke detectors, where the batteries after only half a year gave up the ghost. So I had me to look for cost-effective durable 9V blocks.
Almost exactly 2 years ago I had already once these batteries Duracell Procell 9 V ordered from Amazon. At that time, the packaging of a sealed transparent film, today from a cardboard box, with one pole is protected by a plastic cap. Inscription and colors of the batteries are the same (except, of course, expiration date and serial number =: o)). Now I hope that the new product has the same quality as the batch I then get on Amazon. For the 9 V blocks of time to perform almost 2 years still their service without a would have been. Given the price I am very satisfied with the blocks.