Depending on what kinds of apps I'm running, I get 4.5 to 5.5 hours of on-screen time on my LG G3. Using it at work for the occasional conversations with clients, calendar, calculator, and some light news browsing, I'll get about 5.5 hours of on-screen time. If I leave my house at 8:30 AM with the phone at 100% charge, I'll typically have around 35-45% by the time I get home at 6 PM (depending on how many phone calls I had to take). However, if I run Youtube and do a lot of internet browsing, the battery goes faster. On a diet of HD Youtube videos I can drain a battery in 4.5 hours easily.
Unless LG improves battery performance somehow on the G4, I'll probably sit that one out, especially if the rumors of a 3K display are true. What would be the point of a 3K display when almost everything is still 1080P if it means the battery would drain after 3.5-4 hours of video watching. I hope LG maintains the same resolution as now for the G4, and either goes for a bigger battery or a newer battery with better technology. Other than the hungriness of the 2K display, the LG G3 is an amazing phone.