The My Account area of the app allows you to sign in/out of your NC Software account as needed, although once signed in you should remain signed in as there is no reason to sign out other than if sharing a device with another user. You can view your subscription status for Logbook Pro Mobile and the Airline Schedule Importer and if your app allows in-app purchasing you can renew your subscription directly from this screen. Subscriptions can be renewed at any time as they will extend off of your current expiration ensuring no overlap.