Finding a stolen iPhone with tracking app?

My iphone 4s was stolen last night. I was able to go online and view where it's at. The problem is it's above a apartment complex so the cops said they can't do anything about it because they don't know what exact apartment it is. Well i kept tracking it and noticed they were moving from place to place. I called the police and let them know. They came and brought there own computer guy to track it. They were about to find it, but the phone must of died because it stopped showing up. My question is if the phone is charged will they be able to turn off the tracking? It's being tracked by my itunes account so they don't have access to that. Not only did they steal that, they stole my ipod touch, and some other important documents.

Added (1). I'm using icloud but its only working for me when the phone is on.

Oh that's so sad… If you were using icloud on your iphone you'll be able to track it even if it's turned off… Goto www.itunes.com/ sign in with your account… Click on 'find my iphone'and it'll tell you the exact location. If you were not using icloud then next time use it…

If they reset the phone, then you can't track it.

There are 2 things you can do since it is an iPhone.
1. You can log into iCloud.com and go to Find my iPhone and tell it to make noise, lock or even wipe itself out if you'd like. When the phone is connected to wi-fi or a cellular network it will automatically begin tracking again. Also, they can't disable tracking as it is standard with all iPhones. If you has the find my iPhone app, they can remove it which could cause to to stop showing up in iCloud.

2. You can also call your wireless provider (AT&T, Verizon, or Sprint)
You can select, Report a lost or stolen phone and they will deactivate the device for wireless use.
They will also let you know if they can track it, if they can you may be able to get an address and everything.