http://www.knowyourcell.com/htc/htc-desire...htc_desire.html

does your case collects lint?

3G will drain more than 2G network. if you notice the spec sheet normally they will rate the talktime differently.

3G or 3.5G is the same spectrum anyway, so doesn't make a difference.

in settings->wireless and network->mobile networkS->network mode

there are 3 options:-

GSM (2G)
WCDMA (3G/3.5G)
GSM/WCDMA auto

the last option will always search for WCDMA first, and fallback to GSM if it cannot find one. it is the searching that will cause it to drain battery. so if you are sure that you will always be in 3G coverage and in need of high speed data, choose 2nd or 3rd option.

if you want to save batteries, then choose only 2G.

For some reason after I uninstalled battery time lite from motalen, my battery life seems to improve a bit. Not running any battery widget now.

alternatively you can long press power button and turn off from there.