This highly depends on whether you have WIFI and/or Bluetooth on. In the case they are on continuously, then the battery will drain much faster than when they are off. That important remark aside, the battery of this device is pretty good, although it will depend on how much you use it. E-ink displays consume battery when they have to "update", and only consume a very small amount of battery when they are "idle". Thus, if you intensively scroll and surf the internet with this device, it will last shorter than if you just used it to read books. Considering all of the above, it's clear that it highly depends on the usage, but you can rest sure that the batteries in these type of devices are good. In my case, I usually charge it every 2 weeks.

It depends on how you set it up. The way I use it, as a notepad with 15min until it goes into standby, about 2-3 weeks without problem with use of 1-2h a day.

In my experience, the battery lasts forever, certainly several days if not weeks. As already mentioned, it depends on the type of use, so the question is almost impossible to answer. In my experience, the backlight consumes the most, but you only have it on when it's really dark.

I only need it for reading on the train with low backlighting without WIFI/Bluetooth. It feels like it lasts forever and after a few weeks (months?) I recharge it.