If the G4 battery is in good health, no swelling or physical damage, then expect ~4-5 hours SOT on light, and ~3-4 hours SOT on moderate usage.
My G4 used to give average 4.75 hours SOT in light to moderate usage, but SOTs are subjective and vary from user to user, but G4 battery timings are better than S6, and not bad at all.