Why is my battery time so much shorter after jailbreak? I've been impressed with the better battery time of my new iPhone 4 as compared to the 3G I had before. Yesterday evening, I finally jailbroke the 4, and the battery time today has been much worse than usual. Why is this?

I installed a very few programs from Cydia: FolderCloser, NoLockScreen, SBSettings, biteSMS, PdaNet, My3G. Note that I haven't used PdaNet yet, so I would rule that out as a culprit. Also, while My3G is set up, I haven't actually done any faux-wifi stuff today: no Skype, no wifi-only downloads, etc. I've deliberately used 3G less than on normal days, and not used wifi at all (also not as a hotspot). I've not played music at all today, in fact I've barely turned it on at all! The screen brightness is as usual, at about 70%. The phone was charged to 100% overnight as always. 

Despite this, the battery is already under 40% at 5 p.m. where it would normally still be well above 60%. At this rate, I don't think it will even make it until I get home -- which is worse than the battery life of my old 3G!

What's depleting my battery faster than usual, and how can I prevent that?

Update: The first day of jailbroken battery life must have been a fluke, or was fixed by rebooting. I've been through a few cycles now and battery life seems to be practically unchanged after all.
I can see two main possibilities: 


Apps like FolderCloser, NoLockScreen, and SBSettings shorten battery life by requiring heavy background processes. The only solution to this would be either to not install these apps or restore the phone to its original state altogether (and not have these apps installed). I am convinced that jailbreaking allows for processes that are not in phase with Apple's careful thriftiness of battery use.
Your battery is not calibrated properly so your iPhone miscalculates the remaining percentage. The solution here would be to drain your battery completely and then fully charge it.


Good luck! And know that you can restore the phone to its original state.