Create a new timeline, give it a name (OUTATIME or whatever) and drop in a timeline action that contains the desired timeout action (jump to scene X / start scene X / go to URL X, etc.).
Drag the action keyframe to the right and set it at the desired time-out length (25 years in the future won't work, Biff).
Go back to your main animation and set the time-out triggers - on mouseUp (or any other mouse event): start timeline: OUTATIME, etc. You can also create a background object with a mouseLeave action or whatever.
The mouse event starts the timer over and over again until the last mouse event. As long as your timeout time is significantly greater than the time of any animation, you should be cool. Also, you can place the timer event to be triggered at the end of an animation or timeline or whatever.
This is clearly not anywhere near as sophisticated as a script that tracks mouse movement (and lack thereof), but it should get you through Earth Angel and Not Fade Away.