I just received my Prime, and have been browsing the contents for a few hours. I was checking the advanced grapher's demo images. I was scrolling through them with the left/right cursors (I didn't touch any other key). It appears that the cursor keys do reset the timeout for the backlight intensity (i.e. if the screen gets dark, pushing a cursor key does bring the luminosity back up); but they don't reset the shutdown timer (i.e. no matter how many times or how often I press the cursor buttons, after a while the calculator just shuts off, even if I had just pressed a cursor button).
Is this a known bug?

Cristian

The shutdown timer is connected to a random number generator.

Haha, funny. Considering that a truly random generator isn't an easy thing to design, they apparently did a good job! :)