Extending Battery Life

Someone in my office said that he has doubled and even tripled the life of his auto batteries by filling low cells with electrolyte (sulfuric acid ?) which he purchases from auto parts stores. He said that he learned this "little known technique" from his Dad years ago and that it is a great secret that the battery manufacturers don't want to become general knowledge. He never uses distilled water and said that to get that maximum life out of a battery you need to add electrolyte throughout the entire life of the battery, not just as it nears the end of its useful life. We live in the Phoenix area and our extreme heat is especially hard on batteries. Prolonging their life sure sounds appealing. Can anyone substantiate his claim ?