packageName returns null after 1 hour

[ArpitJ1610]

AppChecker mAppChecker = new AppChecker();
foreground_app_package_name = mAppChecker.getForegroundApp(mContext);

 I am  using the above code to get the foreground app name from service in background. The code works fine till 60 minutes and at 61 minutes it gives null value at foreground_app_package_name .