Are the battery hacks implemented in the 3.16 ROM? I have a settings ROM that adds them for me, so I didn't check to see if they were in this ROM.
If not, do the battery registry hacks, turn off the IR beaming, lower your screen brightness and set your screen not to stay on too long. Those tips should help you minimize the battery drain.
Of course GPS and WiFi will suck down the battery life as others here have mentioned.
EDIT: If you like your phone's like Sir-mix-alot likes his women, you can get an extended battery (Mogul got Back).
3200 mAh - $64.95 plus shipping
http://www.seidioonline.com/index.as...ROD&ProdID=888
3600 mAh - $79 - Free Shipping (better deal IMO)
http://www.wirelessground.com/mogulsuperbatt.html