I know with the 2G iPhone, you could burn through the battery fairly quickly if you were surfing on wifi but it was still a couple of hours.

When at the cottage this past week, I lived with location services on and push & 3G off (the former not needed, the latter not available) and got very, very good life out of the phone, charging every couple days.

I’d only turn it off if you are either already below 20% battery and need it to last long enough to get home/back to a charger/etc or if you’re in a crappy non-3G area.

If you’re in a bad/no signal area for 3G, the 3G in your phone will constantly look for a 3G signal…even in standby which is really ’screen off’ mode since it’s also used for the phone and not strictly data purposes. Similar rules apply for wifi being turned off although it will only search for an access point when awake. With my 1st gen iPhone, I couldn’t notice an appreciable loss of battery by turning wifi off vs leaving it on….it only seemed to matter when you used it. Because of the 6gb data plan, for now at least, I’ve turned off wifi completely and only use it in poor reception areas where I know there is a hotspot - like in parts of my house.

Really? Because it’s likely an apples-to-oranges comparison but I can easily get two days out of a charge on my Treo (sometimes three) here where there’s only Edge, but when I’m in a 3G zone I need to plug it in after six hours.