Allow different times when single clicking

Single-clicking is the easiest way to turn Caffeine on, but it's a shame that it turns on forever. There's a good chance that I will accidentally leave it on for days. It would be nice if it allowed the user to select the default time to remain caffeinated.

I would set mine to 3 hours. Single-click, get three hours. When time is running low, double click and get another 3 hours. Quick, easy, safe.

The right-click Activate For hierarchical menu would remain unchanged of course. This would just make the default behavior a little safer.