Your Libre 2 sensor can collect up to 8 hours of data. For a continuous overview of your results, we would advise you to regularly scan your sensor. You don't need to scan at night as your sleeping time is not affecting any scores. However, to ensure that this part of your active day and perhaps a late dinner is still being captured it makes sense to scan before going to bed.
If you are based in Germany, Austria or Switzerland you have a Libre 3 sensor, your sensor only needs to be scanned once after the application to connect the sensor with the app.