I limit myself to playing video games only during the winter, but I'm realizing that wireless controllers-with their battery-also throttle my play time on occasion. This helps me kind of manage the time I spend playing.
(Also, when it starts to hurt my head one way or the other)
@ScionAltera once upon a time, I took blurry vision at 2am as the time to quit.
But now because I hate being cold, I've decided to spend as much time outside as I can in the summer...and video games aren't exactly complimentary of that desire.
@L_D_G I don't limit to winter only, but I do generally take the controller batteries dying as a hint that it's time to stop for the night.