well if you turn off some of the stuff you dont use all the time, like GPS and using the network to locate you, and in my case 3G and wifi since im not in a 3G area most of the time, im able to get a full day out of my G1 with no problems, and thats with moderate to heavy usage, just depends on the day.
Now i always plug mine in at night, because i use it for work and am on call and cant find myself with a dead battery, but usually im between 20-30% when i plug it in.
i didnt do any training, or any of the other stuff people say to do.