It is not so much Exchange but more just having the 3G connection on 24x7.
You can try (only speaking from personal use of version 2) going to settings, then one of the top options is "fetch new data" (or along those lines) and try to turn it down slightly so it checks in a lot less frequently.
That being said, I can not say if the 3g connection won't drain the battery if it is just on but not fetching data. - You may want to see if there is any way to disable it / set it to on-demand.
Edit - for reference, I had a Sony Ericsson phone with 3G, the battery lasted around 3-4 days, however if I kept MSN messenger working in the backgruond with 3G on, I was lucky to get ~12 hours.
true, it's not exchange, if you have an iPhone 3G(s) and want to use all the bells and whistles, get used to charging the battery 2 or 3 times a day, here are some not so serious tips :) http://37prime.wordpress.com/2008/07/13/how-to-drain-iphone-3g-battery/
– None – 2009-09-01T14:53:33.007Push notifications, for any iPhone app, are a killer for battery life. I find setting it to an hourly fetch means I can go a day or two without charging. – jwaddell – 2009-09-03T01:18:24.163