I am using core location framework inside my application and I set the location string in UIBackgroundMode or Required background modes(in Xcode 4.2) for getting the updated location from didUpdateToLocation method when app is running in background and also sending this updated location to server by hitting the specific link inside didUpdateToLocation method of core location framework.
My question is that will the app be terminated after some time when running in background or not?
No, there is no specific time defined for this.But app will definitely terminate based upon certain parameter - battery drain, memory footprint issue etc.
In developer documentation it is clearly mentioned - "The system keeps suspended apps in memory for as long as possible, removing them only when the amount of free memory gets low. Remaining in memory means that subsequent launches of your app are much faster."
Go through this for complete details - http://developer.apple.com/library/ios/#DOCUMENTATION/iPhone/Conceptual/iPhoneOSProgrammingGuide/ManagingYourApplicationsFlow/ManagingYourApplicationsFlow.html