Welcome to reality...
This is because of the test setup: Reader upright, no motion no touchscreen. Switch on and after booting remove power. Turn a page every two seconds until device turns off.
Just be happy about the awsome time between charging cycles and go to the next electronic market and buy a cheap USB wallcharger that delivers more than 1000mA so you don't need a computer to recharge.
BTW nearly everyone here made this experience to a more or lesser extent