I clicked through the link, and now my brain hurts!
10=yellow
312=brown
13=orange
625=blue
Newer aids will give you a warning that your batteries are dying. Using the warning is supposedly 30 min. before the batteries actually die. If yiou go by that and Davidb’s link then it would mean it’s safe to wear your aid with the current batteries until the warning sounds, in other words don’t switch batteries early.
I read the article and I’m not sure I know more now than I did before I read it. 
One thing I got from the article was that that high power batteries used in a scenario where the high power requirements aren’t needed can produced shorter battery life than non-high power batteries.
I am not sure what conclusion to draw regarding the varying current requirements of the aids and the voltage produced by the battery in response.
I’m just finishing up my first week with a pair of Costco Kirkland Signature Premium aids (Rexton Gem 12 RIC BTEs) and the size 10 batteries lasted about an hour shy of a full 7 days. I wear these aids about 16 hours a day, and do switch between 4 programs every day.
I did not notice any deterioration of sound quality or volume, but over the last day and a half, the wireless communication between the aids was not always immediate. After hearing the 2-beep low battery warning the 2nd time in about 10 minutes this evening, I swapped out both batteries.
I was surprised the volume control setting that I’d set earlier with the remote stayed in both aids. I expected them to default back to the starting volume.
Did it stay on the same program or did it go to program 1?
They were in program 1 at the time, before and after the battery change.
Got my hearing aids last Thursday afternoon and they use a size 13 battery. I am using my aids between 12 and 16 hours per day. I am still on the original set of batteries. They are Rayovacs. I would not be surprised to find that I experience a shorter battery life as the aids are powered up. By “powered up,” I am referring to the fact that I am first time hearing aid user and my audi provided an initial setting that does not take advantage of the full gain that can be produced by the aids. I go back in a week for a follow-up, at which point I believe she will provide me with the ability to use more of aids’ capabilities, which I would suppose will result in a faster drain on the batteries. This is purely speculation on my part as I won’t know for sure as to what I am saying is true until I see what actually happens.
I wear mine from the time I get up till I go to bed…about 17-18 hours a day…
I use 312’s and I get 9-10 days till I get the beep. I switch both out at the same time. I have a little more warning because my remote will show me battery life.
As far as sound quality …If I change it at the beep sound is just as good as when I first put them in. If I wait longer I can tell a little difference.
My first batteries were the Costco batteries that lasted almost 7 full days. The 2nd set was Eveready EZ-Change that are a year plus old, and they lasted only 6 days. The right side (better ear) went first this time. I still did not notice any deterioration of sound quality, but wasn’t around live people to notice. And this time, both aids reverted to the default volume setting when new batteries were inserted.
I am just starting using the Rexton from Costco with the remote. I turn the remote off when not using it and figure the batteries will likely last many, many months.
I think I’ve seen the AAAA batteries at Fry’s Electronics but haven’t looked since I got the Rexton last 2 weeks ago. Of course you might live where there are no Fry’s Electronics so you can buy them online though you’ll have to pay shipping costs. $.99 or $1.99 for a 2 pack depending on whether you want a lesser known brand or a “mainline” brand. Since I live where the stores first started and there are at least half a dozen Fry’s Electronics stores within 20 minutes of me I forget that some don’t have easy access to them. I wouldn’t be surprised to find them at Long’s Drugs and Walmart or the like as well.
Here’s the online info from frys.com:
I am wearing a set of Oticon Duals XW. These are new as of 10 days ago. Battery life is said to be 10 days. Understandably my batteries only made it to day 8. WOW what a huge difference in how these performed with fresh batteries ! Perhaps a change at day 6 would of been best for these aids ? Since the aids have gone through their learning stage i expect to hit day 8 however ? I truly believe the batteries performance was degraded well in advance of the Oticon XW’s low battery warning. The degraded batteries really made the performance take a steep dip .
Interesting battery discussion. I use 13. Started out w/ PowerOne GenX and then to Rayovac 13 and now back to PowerOne GenX. I’m wearing Phonak Exelia P, BTE…burning up batteries way too fast, esp w/ even a few minutes of phone use the HA on the ear I use for phone goes much quieter. Not dead, just quieter. Rest of discussion here
http://www.hearingaidforums.com/showthread.php?t=3644
Basically, even w/out phone use my sound quality degrades and I have trouble w/ word recognition after 3rd full day on batteries. Mine should last at least a week and possibly up to 10 days. Audi can not figure it out, so it seems it is up to me???
I don’t know if you folks are using anything like the Phonak iCom, Oticon Streamer or the various other Bluetooth type devices - if so, remember that use of these devices will decrease battery life.
Yes mine is bluetooth. They are rated for 10 days of use. I would be happy with 7 or 8 if that is the case. I just found that the sound quality was degraded well before my aids gave me the low battery signal.
This must be the normal based on my experience as well.
I’m trialing an iCom as of this afternoon. My battery life in the HAs will be shorter. However, audi is going to talk to someone at Phonak to figure out why even w/out iCom my size 13 batteries are only going for 3 days before audio quality degrades. In “normal use” these 13 batteries w/ Phonak Exelia should go up to 10 days. This has been confirmed by so many ppl. For sure the minimum should be a full week of every waking hour use. Did find out that changing programs on the HA would be a major drain of power…but we agree that isn’t the answer. Stay tuned…
I’m wearing Starkey Destiny 1200 CIC’s which are expected to drain batteries, according to specification sheet, in 3 to 5 days. Mines get depleted after 4 full days (4 x 24 hrs), performing perfectly the first 72 hours and gradually declining in the last 24 hrs. I wear them 17-18 hours a day, from the moment I wake up until I go to bed (I sleep 6-7 hours).
Conclusion: I change batteries every 3 days when I wake up and take the aids out of the Dry&Store. Thus, I assure my aids 3 full days of perfect performance (as batteries are being used less than 72 hours). I want a clear and perfect sound, as I get very stressed when the power is fading and I start hearing less.
It seems all they all beep low BATT one day late. Wonder if all brands come from the same factory in China. 
Here’s a handy link I found which will can tell you what to expect from your HA in regards to battery life expectancy.
http://www.audiologyinfo.com/battery/abbot.htm
So…going back to the original question…zinc-air batteries do drop voltage over time (seeing the graph that someone mentioned in audiologyonline web site) which will lead to a drop in output volume. In my case it is noticeable ‘after’ you replace the batteries with new one.
Having digital aids won’t make a difference - digital technology means that the signal processing will either work or it won’t, but you still have to convert the signal to analogue and volume is voltage dependent.
Cheers,
Tony