I was so surprised to stumble across this thread. I haven't received an email about updating my Kindle Keyboard since February 2016. I had to search my old posts to find out when I last updated it.
https://www.mobileread.com/forums/sh...rd#post3253328
I still use my Kindle Keyboard briefly but regularly. I try to always keep the WiFi and 3G turned off. I'd really rather just leave it as it is and not risk any update since I don't have any problems with it.