Timeline Jump Distance Change Pressing Shift+Up arrow/Down arrow causes marker to move 10 frames in a given direction. This being in the timeline that is. 

What I'd like to have it do is jump 12 frames to accommodate half second intervals. 

Attempting to keep robust animations.
In User Preferences (Ctrl+Alt+U), go to the Input section. In the search field on the right, search for shift up arrow (be sure to set your Filter Type from Name to Key Binding). You'll find the binding for the Frame Offset operator. If you expand the operator, you should see a Delta setting in the lower right. It's default value is 10. You can change it to 12 (or whatever other value you want).