All the ROMs do a pretty good job. If battery life is your #1 concern and nothing else matters:
1. keep screen brightness on minimum. Screen filter can reduce brightness even more.
2. If you use wifi, set it to sleep unless charging.
3. Don't use 4g. Use 3g only.
4. Disable syncing or data entirely and only manually sync when you need to. (Something like JuiceDefender can automate this)
5. Disable google backup.
6. Disable GPS and verizon/google location services.
7. Disable bluetooth.
8. Check and eliminate all wakelocks using betterbattery stats.
9. Turn off all haptic feedback.
10. Freeze all Samsung and Verizon related services using titanium Backup.
11. Maybe a mild underclock on your kernel.
At this point, you will get great battery on your dumbphone with a giant screen