To preserve battery, my kindle is in constant flightmode which turns off wireless.
Every now and then, amazon releases a update for kindle, but the device isn’t downloading the update if i turn on wireless for a while.
If i download the update by myself, it only needs a few seconds thanks to my fast internet connection.
To install the most recent update for your kindle, simply plug your kindle with the suplied usb cable into your computer go to this page and download the file directly to your kindle.
Then unplug your kindle and open the kindle menu. Open the menu again and press update kindle.
Now wait a few minutes while it installs the latest software and your done.
This is a great way to get new features, bugfixes or performance and battery usage improvements for your beloved reading friend.