I've noticed a definite slow down of the phone when in power saving mode, and I only use it when I'm around 20% and need it to last, which has been only a couple times thus far.
Unplug Note 4 from charger around 430 AM when I go to the gym. Do not plug back in until I go to bed at night around 830 PM (not ashamed). When I plug in for the night still have at least ~70% lift left. Battery has been a nice feature of this powerhouse.
Hmm, I've used it 24/7 since I got the phone. What all slows down, if you don't mind me asking? Maybe I should try not using it and see how it does.
more lag, stutters when scrolling through stuff. Things like that . . .