"Registration" for an ionic app using phonegap-push-plugin

Hi,
I developed an ionic3 app that uses phonegap-push-plugin in order to recive push-notifications.

Does anyone knows how many time do I have to call “registration” like this

pushObject.on('registration').subscribe((registration: any) => console.log('Device registered', registration)); 

a) Do I have to make a “registration” every time I open my app?

b) Or is enought only once after first installing the app?

… and why ?

Thanks.

is enough only once after first installing the app?

Thank for the answer.

According to this link https://stackoverflow.com/questions/20910803/register-a-device-on-gcm-every-time-the-app-start-is-the-right-approach
a more comprehensive answer would be:

  1. Every time the app is updated
  2. When the phone restarts

Is it possible, beside these 2 cases, to have a third namely “when OS is updated”?

I believe the phone restarts when OS is updated