I understand what you are saying Tomsen. About 5-6 months ago Amazon Stopped Supporting the Older Fires. My Fire 2012 & my Phone

1/2 the Apps that use to work Stopped & they don't work on the New Fire 10 either. So it Buyer Beware IMO
Since this Thread was about Battery Life That's ALL I can Say that even works any more. OP should Ask What Works on the HDX...