I get good battery life with aospCMod, have you tried tracking down what is draining your battery? Look under settings>>applications>>running services and see what's running in the background. Look under settings>>about phone>>battery status then click on the battery graph, and on the next page look at the bar under the battery graph, if it's not green, you have signal issues.
The best ROMs for battery life are Harmonia and Rodimus, but every ROM can be tweaked to have almost identical battery life.