Theoretically I have adjusted the persistence time for on-screen Notifications in Sierra on my MBA. I get confused and tend to click on them rather than swiping to make them vanish.
I don't mind them being there, I just object to how long it takes for them to bugger off. A Google search gave me this solution: Open Terminal and enter <defaults write com.apple.notificationcenterui bannerTime n> with "n" at the end being the desired number of seconds. Then logout & back in or restart.
It seems to have worked out well. Just had a notification pop up & vanish in 2 seconds, as selected. It's enough time to register the arrival of a notification and take in the content before it goes away.