Well, I won’t tease you: yes, it does!
I recently decided to jailbreak my iPhone 3G(S) for the first time – having plenty of experience doing so with my old iPhones (3G and classic) and the iPhones and iPod Touches of firends and friends of friends.
I used the „official“ jailbreaking method, provided by the DevTeam: Pwnage Tool.
Almost directly after jailbreaking the iPhone I had the impression, that I could watch the battery indicator fall.
After two days, the battery was running on empty. Although I had it plugged into my Mac several times in order to synchronize it. I hardly ever plug the iPhone in to actually charge the battery. I do so in order to sync it and it gets charged „accidentally“.
This tactic worked well ever since I got my 3G(S), so that this experience really left me… bewildered.
And it made me setup this experiment:
Step 1: I un-jailbreaked the iPhone again, setting it up as if it were a new device (meaning: I did not use the backup iTunes created earlier, when asked).
Step 2: The experiment started on last monday, 8 a.m. after having the iPhone plugged into the wall socked for about 6 hours – completely charged.
I used the iPhone no different then before: I’m listening to the iPod for about 2-3 hours per day, receive between 40 and sixty mails via „push“ (Google Exchange) and about 30 „other“ push notifications (Boxcar, …) and use it as an actual phone for somewhat between 5 and 10 minutes per day. As described above: I don’t explicitly charge the iPhone. I sync it with iTunes and leave it plugged in a couple of minutes while doing so.
Step 3: On tuesday evening, the iPhone was charged to about 40% and I entered phase 2 of the experiment: jailbreaking it again.
Step 4: Again, I used Pwnage Tool to jailbreak my iPhone. Again, I charged it for almost exactly 6 hours (wall socket) and then started using it as usual until thursday evening. At least that was what I had planned. At 4 p.m. on thursday the battery was totally drained and the iPhone decided to go bye-bye.
Step 5: I decided to re-do the test in a shorter version over the next (now: last) weekend using a slightly different setup: I disabled all push services and disabled my mail account on the iPhone.
Saturday was going to be the „Steve day“, Sunday the „jailbreak day“.
To cut a long story short: after a testing period of 20 hours on each day and almost exactly identical usage, the iPhone had about 19% higher battery charge level on the „Steve day“.
I dare not to say if this is what everyone will always experience when jailbreaking the iPhone 3G(S) – but this is what I got.
As of today, the iPhone is still jailbroken. However, what do I really get from it (things I really want/use): xGPS as a zero-cost alternative to buying Navigon and/or waiting for Google’s navigation solution… and… well… the hope for a tool that re-enables the tethering option in a non-scary way. So I guess, I’ll wander back to steve-land this evening…