$ defaults write com.apple.notificationcenterui bannerTime -float 0.8
$ defaults write com.apple.notificationcenterui bannerTime -int 1
$ defaults delete com.apple.notificationcenterui bannerTime
To test it
$ osascript -e 'display notification "test notification!"' 0.1
Ref: https://osxdaily.com/2014/01/29/change-notifications-banner-time-mac-os-x/