Do you have a Blackjack?
3G on the Blackjack is brutal on battery life. And the push email results, given higher email volume, in a lot more 3G data transmission.
You can go two days in an EDGE area w/o charging a Blackjack. Most won't make it 8 hours in a 3G area w/ push and heavy email.
Nope no blackjack, no MS operated device really works for me and my emails, I use the "teentoy" Sidekick which is fantastic on what it does, but yes very limited as to what it really can do

But for the data price, and keyboard, and nice "parallel runing prgs" it has beat everything else so far as my "daily driver" and trust me I've tried everything from $200 Tmo Dash to $2000 OQOs

Well your black jack actually is not telling the truth, since it is OFFLINE really most of the time, as soon as you want to start browsing it will reconnect, stick Skype on it (which communicates constantly) and see how many hrs it does, I can bet you, you won't pass the 4hr mark. There really is no device on the market that will do REAL 8hrs with 3G!