Notifications in Windows 8 are shown on the top right-edge of the screen, instead of the usual balloon notification in the system tray. By default, the notification stays on the screen for 5 seconds. If you want them to stay open for a longer duration, this is how to do it.
From the desktop, move your mouse pointer to the right-edge of the screen until you see the Charms bar. Click on Settings.
Then click on “Change PC Settings”.
This will open the Modern Control Panel. Click on Ease of Access, and from there adjust the notification display time as shown below. Unfortunately, the lowest you can go is 5 seconds.
If you don’t like the Modern Control Panel, you can do this from the traditional Control Panel as well.
Press the Win+X or right click in the bottom left hand corner of your screen to open the WinX menu, then launch Control Panel.
Click Ease of Access, then click on Ease of Access again on the next screen.
Now click on the “Make it easier to focus on tasks” link.
Scroll down the page. Here you will be able to adjust how long Windows notifications stay open.