There's been a lot of concern over MSFP and how it affects battery life on Windows Mobile devices.  But w/ the MSFP update rumored to be around the corner for the Motorola Q - a device already tight on batter life - the debate has spurred up again.  Here's some info on the subject that will hopefully calm some people's worries that PUSH email is to blame.  That said, I'm very interested in the issue so if you have any solid info beyond a hunch, please let me know.

Here is how MSFP works on the technical side from the Exchange team that developed it:
- http://msexchangeteam.com/archive/2005/06/07/406035.aspx
- http://msexchangeteam.com/archive/2006/04/03/424028.aspx

From Jason’s blog entry:

by default the heartbeat is every 15 minutes but is self tuning. The heartbeat is about 309 bytes which equates to about 1 MB over a month.

In general, it IS dependent on your email use.  That said, the heartbeat IS overhead, but depending on its setting it should be minimal compared to the actual email you pull down.

To get an honest baseline, you would have to set your device in a fixed location with a fixed signal, and repro the exact emails.  So just about ANY battery life comparison tests you do won't really be valid.

What I suggest is turning PUSH off, and running w/ some time delay, let's say 10 minutes.  Then the next day when you'll be doing about the same thing (ie: sitting in your same office), try using PUSH again.  If you receive about the same number of emails at regular intervals, you could get a feel for the net difference in battery life for JUST PUSH.

You also need to consider that other fixes on the device from the original ROM and the new MSFP one may have affected batter life regardless of your email settings or useage.  In general if they did any radio stack work or tweaked any power settings or timeouts, etc, there would be a difference.  I know they work really hard to IMPROVE battery life with these changes, but there's always a chance of regressing.

Also note that setting email notifications to vibrate eats up tons of battery power since the motor is power hungry.  MikeCal has a great post about LEDs and the Vibrate motor killing your battery life.