Just so we can get some more stats, I'll chip in what I come up with. I'm about to hit up some iHop as my iPhone just finished charging 100%:
2G Jailbroken & Unlocked (AT&T)
Wifi: OFF
EDGE: OFF
Email PUSH: OFF
Notifications: OFF
Location Services: OFF
Brightness: 100% + Auto (I've used this all the time and usually still get 2.5-3 days with a charge)
Possible background processes: Winterboard
Possible daily usage: Music, Calls, Text
I will refrain from Apps, Games, and Videos and see how long I can get through. I made a thread about a similar problems, but after checking my Mial settings (for the first time), PUSH was on, fetching 15 minutes, so I thought maybe that was the problem. But now its off (and I never got any push notifications either so I didn't know).