Yup, my biggest increase in battery life came when I changed my email-checking frequency.

Just a quick note about that for Phil: Originally I hadn't realized that it would still check email at the moment I opened up the email app. At first I thought that it would *only* check mail at the timed frequency or when I pressed the refresh button. When I later noticed that the act of opening up the email app would start a connection and do a mail-check, then I didn't mind decreasing the automatic-checking frequency.