Here’s my take:
Your GPS does RAIM continuously. If the monitoring fails you get GPS PRIMARY LOST.
Depending on the type GPS installed and operational configuration your onboard GPS can compute future RAIM. If you look on the predictive GPS page you will see 5 minute intervals of the destination or any pilot inputted waypoint . A “Y” means GPS will (should) be available for navigation.
What the box can’t know planned outages. Therefore we check NOTAMs at our destination, cross check them for time and approach planned to determine if GPS will be available to fly the approach.