What is the expected battery life for a hearing aid with moderate wireless iPhone use?

Based on your question, I'm assuming you are using some type of audio streamer with your aids or using one of the newer Bluetooth direct aids.  More info is needed to properly answer but I'll attempt to give a general idea of battery life and what impacts the battery's duration.  The power draw required by the aid determines the life of the battery. There are several size batteries used in today's aids with the smaller lasting fewer days than the larger. They rank in size from the smaller #10 to #312 to #13 and to the larger #675.  The greater the hearing loss, the more power required for amplification. So if you have a moderate loss and use an iPhone moderately, you can probably expect about 4 days to a week with the #10, a week to 10 days with the #312, and 10 days to 2 weeks with the #13. The #675 is usually reserved for power aids to fit severe to profound loss therefore not a part of this equation.  The more hearing loss you have, the more battery power is required and the more you use your phone, the more need the aid has for power. So there's not an exact answer due to the many variations in usage. Hope this helps. 

Battery life expectency really depends on size of the battery, if the patient is shutting off the hearing aid when not in use and how often the hearing aids are worn. We typically find patients batteries last anywhere from seven to twelve days.

There can be many variables that can determine battery life from the size of the battery (capacity) to the type of wireless connection to your hearing aid (direct to iPhone, or via a streamer or via T-coil etc.) to the type of hearing aid (in some hearing aids the battery may last 2 to 4 days, in some about a week - I haven't seen any batteries last more than 10 days for some one who uses their hearing aids over approx. 8 hrs a day).

One viable and good option to consider is to use a rechargeable technology if there is some concern about using "throw away batteries" and recurring cost. There are some hearing aids that can be retro-fit with rechargeable hearing aid technology; you will have to consult an audiologist to see if that's possible - Z-Power make s a re-chargeable technology that can be fit on certain models of hearing aids.

One of the most important questions to ask would be what is the size of the battery? The larger the battery, the longer the life. For example, a power behind the ear hearing aid with a larger battery will have more power compared to a hearing aid with a small size 10 battery. Another consideration is the degree of hearing loss. Also, if you have an intermediary device (neck loop), it will consume slightly less battery compared to direct streaming from a device... On an average one could say anywhere between 5 days to 9 days... Hope this helps....