I leave my phone on 4g all the time and get ~13 hours. I tried only 3g and my battery life was significantly less. IMO there isn't a built in switch for a reason.
That's where you're wrong, there is a built in switch in the settings, people are just looking for a widget. You're probably the only person who says they get better battery with 4G, honestly it doesn't even make sense. If I disable 4G and only use 3G (like I did yesterday because 4G was down) my battery was significantly better, it didn't hit the charger all day, on 4G I would've had to charge my phone at least once probably twice
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