Here is the documentation for the IsolStorageSettings.Save method dated February 14, 2014:
http://msdn.microsoft.com/en-us/library/windowsphone/develop/system.io.isolatedstorage.isolatedstoragesettings.save(v=vs.105).aspx
And an excerpt from it (see Warning):
However, you do not need to call the Save method on Windows Phone. Data stored in an IsolatedStorageSettings object is saved automatically.
My experience as a developer also proves that - settings are saved automatically without the need to directly call the Save method. But note that this only happens when you close the entire application, as indicated on MSDN:
The data written to the IsolatedStorageSettings object is saved when the application using the class is closed. If you want the application to write immediately to isolated storage Save the method in the application code.
source share