Just sharing my own battery life study. I received my KS9s 385 days ago and I have always used Costco batteries. I kept every battery I have used and I just counted them today. I have used 174 total batteries in 385 days which works out to 4.425 days average per battery. Not too great.
I wear my hearing aids all day, every day for approximately 14-16 hours and I stream my phone, iPad and tv.
Hopefully someone finds this information useful.