recently got my iphone replaced by apple due to bad battery life. so far it's holding up good, though I didn't have the time to JB it until now. will do so tomorrow.
for me, unjailbroken, fetch on, push off, pretty heavy internet usage: 4hrs of usage plus 40hrs of standby.
But since I'm back from my vacation I will return to my normal usage and to a jailbroken iphone, let's see how it holds up then ...
I just got my iPhone 3gs 2 days ago and my battery only lasts about half a day. I am on it alot, but is this normal? Considering I only got it two days ago?
A lot depends on usage and how u have things setup, and what iOS version ur on...I have 3GS on 5.0.1 and I can get at least 2.5 days of standby and at least 6 hrs usage..
I now have untethered JB and pretty much everything turned off that can be..I leave Bluetooth location services wifi off till I need them...iCloud is disabled...push is off, notifications is off for most apps except SMS calendar and a couple other apps.
Brightness turned way down.. And the auto setting in brightness turned off..
Check your "Settings - About - Usage" statistic occasionally. On my 3GS before I got my battery replaced, I could usually estimate about 20% battery drain per 1 hour of active use. Moreso if I'm playing games, less if I'm just checking Twitter every so often. This is with brightness at around 40%.
If it's draining significantly faster than that, you may have an old battery, or maybe something is running constantly and screwing you up, in which case a full restore (not restoring from a backup) may help.