@iancull
Since it's Sense their is probably a widget that will turn off 4G. There was one on the Droid Incredible under Sense Widgets / Tools or something to that effect.
@everyone else
Here's what you guys all need to realize: HTC radios suck the LIFE out of your device even if they are not grabbing data. The display does drain as well, but set that to lowest brightest except in direct sunlight and you'll be good.
DO NOT use task killers. As many have stated here, they do more harm than good. If you aren't afraid to root, use
Autokiller instead as it is a
memory management tool as opposed to a task killer.
DO use
Juicedefender. Before you guys came to that conclusion on this thread, I was going to mention it here. I am reiterating because it's that important to have -- it will literally save your battery.
Last, but not least, in an effort to save battery life,
you should root. I know this isn't the best solution, given that a product should work as you expect after purchase, but in the Android world, I've found this is a necessity.
Get setCPU and when your screen is off set the CPU down to the lowest clock speed e.g. 100 mHz. That'll save you A LOT of battery life when it's not in use as Android loves to clock up to 1 Ghz for menial tasks even when the screen is off!
If you have any questions don't hesitate to ask. I was where you all are last year with the Incredible, and know how to get these devices to last, even on a crappy battery like the one supplied (1300 mAh was all we got back then from HTC).
This is why I love Android -- it's ALL about the community.

-Elo