Re: Bye bye battery
Coverage has a huge impact here.
I spend 99% of the time with my phone on 2G. I only switch to 3G when I need to, which is very rare as I switch on wifi first.
Where I live 3G will murder the battery. The 3G signal here is very weak (or just MIA!). 2G isn't much better, but at least it exists.
This causes a problem for the phone in that it will ramp up the radio to higher power in an attempt to contact a tower. If the tower is uncontactable (as 3G is for me most of the time), the phone remains on high power trying negotiate a 3G link.
The phone will always use the lowest power it can to talk to a mast, so having a mast it can talk to is far better than trying to contact one that just isn't there.
If you don't believe me, get on the underground (assuming your chosen line has no coverage) and see how long your battery lasts. I forgot to put my phone into flight mode once, and it was a painfully slow trip (breakdown)... Result, 50% battery gone in 40 minutes. On the surface I rarely do 50% during the entire working day.