Questions:
Battery life: I have to change the batteries about every five days, The first years supply comes with the purchase
Volume: since it is programmable they can do a lot, I have three different programs, and they can set each one different. They hook a computer up somehow through the battery contact and then there is just a very wide range of how they can change the programs. I have had it adjusted several times and it's very touchy and hard to get it exactly like you want it. But volume is no problem there is plenty of it but if you give it too much you get too much background. The audio guy has been very nice, never seems to mind me asking him to tweak things a little.
I have been using the aid since Sept. of 06 and they have a two year warranty and will replace them once should you lose or damage them in that two years period.
Life expectancy, I don't remember exactly what he told me but I think he said they could last as long as ten years with good care but that the technology is moving faster than that.
You did not ask but don't mind telling what I paid. It was $2400 and the company in Interton and I think he said that they are in Germany