The lifespan of a hearing aid depends on the quality of the hearing aids and how well you treat the hearing aids.
Lower Quality hearing aids may only last 3 years while some higher quality hearing aids may last 7 to 10 years but the average lifespan of hearing aids is between 3 to 7 years.
So if you take care of the hearing aids and avoid getting them wet they should last 3 to 7 years depending on the quality of the hearing aids.
The in the ear style hearing aids tend to have a shorter lifespan than the behind the ear hearing aids for some reason.