Have you checked the battery life? I checked mine recently for the first time. I’ve had this S4 since release day so I think it’s retained decent battery life. I use the workout app/NRC almost daily. I think WatchOS 8 has given it new life and speed as well.I have found the battery life on my S5 is terrible.
I sometimes have to charge it a few times a day. When I went out today it was at 100% but when I got home 8 hours later it was less than 50%
Hope the S7 is better