How Can I Speed Up OS X Notification Center?
Staring in OS X Yosemite, you will find a number of widgets included by default in the Notification Center. You can remove them to speed up various processes. Just click the Edit button at the bottom of Notification Center (you have to be on the Today tab to see it), then click the red minus symbols next to each widget to hide them from Notification Center. You can always add them back later.