MacOS – Configure macOS Notification Center Banner self-dismiss time

That login banner is a provided aspect of the Game Center API in the iOS SDKs, as far as I'm aware there is no way as a developer to disable it from opening when the Game Center login completes. As a user, there is certainly no way to disable it, because it is part of the application's compiled source code.

However, note that it's not the banner that is causing the delays and skips. It is actually the entire login process to Game Center. My only advice is when you open a game that has Game Center logins, open it up to the first functional screen, and just wait the ~5-10 seconds it takes to reveal the Game Center banner. After the banner has displayed and disappeared, proceed normally and you should not be affected any further.

Although I never usually have any luck finding them, I used MacWorld's guide, "How to find hidden preference settings", and I was able to find the hidden preference:

defaults write com.apple.notificationcenterui bannerTime <SECONDS>

Type the above into Terminal, replacing <seconds> with the number of seconds you want the banner to last for, and press return. Then, log out and log back in to reload Notification Center.