No automatic frontlight adjustment as Adoby so poetically put it
For me I set it to 1 bar when reading at night without any external light (otherwise I hardly need it) and I even find it too bright in complete darkness (just before sleeping) so I set the Kindle app to white text on black background which makes it smoother on my eyes.
I recharge every 3-4 days but I download and read quite a few mangas which probably uses more battery than reading books.