Most people can learn to benefit from using hearing aids. How long it takes varies from person to person, depending on factors such as age, physical condition, level of hearing loss
The first hearing aids did not require batteries at all. They were called ear horns and basically were funnels for the ear - scooping up and concentrating as much available sound as possible as you held it up to your "good ear".
World Hearing Day is held each year to raise awareness on how to prevent deafness and hearing loss and promote ear and hearing care across the world.