Welcome to Android Central! It all depends on what you're doing. 4 hours of SOT is pretty normal if you're using your phone like a normal human being (i.e., turning it on every now and then, using all kinds of apps, making calls, etc.). 8 hours of SOT can happen when a person is only watching a video non-stop, without doing anything else (to give one example). That's how the battery life tests in reviews usually report these kinds of figures, and it never reflects real world usage.