AdMob NativeAd should be loaded every time it is shown?

Question

I have a screen with a deck of cards. I want to show the user a nativeAd after a number of swipes. What would be the correct process to load and show the ads?

Let's assume I have adUnitId “xxx”, every time I show the user the ad should I perform a load with id “xxx”, then a dispose when the user swipes the ad and repeat these two actions every time I need to show the ad?

Or can I call the load only once and use a boolean flag to show the ad and hide it, without performing the load process each time?

I have the same doubt regarding showing an ad within a scrollable list.