I have an NFC tag at my front door, whenever I come home, I tap it to turn my N4's wifi on, and vice versa when I leave. I try to be on wifi as much as possible, even though I have the old unlimited data plan, there's no point in testing it.
Another way I keep my battery lasting is the screen brightness. I keep mine way down. Unless you're outside all day, there is no reason to keep it any higher than this:
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And even if you are outside, it only needs to go up a little.
I have not noticed really a difference at all in battery if I leave WiFi always on or turn it off when I am not connected.