My phone never gets warm, ever.
but, I control what works and what don't.
If I don't need it "right now", it is turned OFF.
If the phone's screen is locked, everything is turned OFF. No internet, no sync, no nada...
One exception, I always leave Location ON and in High Accuracy Mode. Takes less time to get an accurate locale.
If the phone's screen is unlocked, then the internet is turned ON, but nothing else.
I activate an app and use it, turn it off when I'm through with it.
Not only does it run cool as the ambient temperature, but the battery life is extremely good.
when idling and the screen is locked, the battery use is on the order of about 8% per 24 hours. ( that means the screen never did get unlocked )
Typical use for me is about 35% to 50% battery use per day from 0500 to 2200 hours, but that is only on days I am out working.
when I am home, I use the desktop PC and the phone sits unloved....