How can I change banner notification time on a MacBook with OS X 10.10.5? How can I go about changing the time that a banner notification stays on the screen before disappearing?

I did some research and tried the suggestion found here, but am having no success on my MacBook Air. I restarted and logged in/out of my account a few times after re-entering the command with no luck. Does this command no longer work?
You cannot easily customize the time anymore on current os since the preference has been removed since MacOS 10.10 Yosemite.

If you want your notifications to stay on the screen until you dismiss them, you can do the following:

Go to
System Preferences > Notifications

Select the notifications you want not to be dismissed automatically. Change the "alert style" to "Alerts" instead of "Banners".