There's no reason for the app to be killed if it has background location tracking functionality in the Info.plist file and doesn't try to abuse the benefits of that permission.
I'm not sure what's your use case for the tracking functionality, but -- together with an assumption that if there's no record from some period, the tracked device didn't change the location -- setting a distance filter would allow to track the location all the time.
That also allows to put a smaller burden on device's battery, because in certain activity types handled by CLLocationManager
, the device may put the location service in idle state if it doesn't detect any significant movement.