Stop the presses. Like any device the Kobo Glo is not good at giving you an acurate detail of it's battery life from the get go. You have to give it a full charge and then let it run until it dies. The software should then start doing a better job of being able to keep track of how long you can go without charging.
I get several weeks out of a charge on mine. All my books are sideloaded (sorry Kobo). I have found issues with it not warning me though that the battery is getting low. I will be reading and suddenly Boom the screen comes up to say plug me in. I have also noticed a difference based on the quality of the charge it recieves. When I tried giving it top ups from emergency battery powered chargers or questionable plugs in foreign countries I had issues with poor battery life and freezing. Once I got my baby back home and charged on a regular adapter it was fine.
Of course certain things will doom your battery life. The biggest is leaving the wifi on. I never bother doing a full power down and I always use the glo light. Mine lives in sleep mode thanks to the sleep cover. It finds a charger once every couple of weeks for a night (when I think of it).
I hope this helps.