This is what I did to greatly improve battery life on Fission ROM with D2G...
I was about to give up on the D2G as a daily user since the battery life I was getting was much worse than the D2. I somehow managed to greatly improve the battery life.
I did the next 3 things at the same time so I am sure some helped more than others.
Install the SIM card fix from FRM
Set radio to CMDA/EvDo Auto
Used SetCPU to set clock at 1GHz
Then I "conditioned" my battery with the following steps
Charged phone completely with outlet, not usb
Wiped battery stats in recovery
Let battery drain all the way down till phone powered off
Fully recharged battery.
My batttery life has been greatly improved since then and now I feel more comfortable using the D2G has daily phone