metricfun: I'll keep an eye on the groupings, since I'm pretty sure it's every 12 hrs. Was the last change approximately an hour and a half ago for you? Do you know?
Edit: There's actually a counter for 12 hrs on the top right of the groupings (if we're talking about the same thing). So I got my answer.
Bundles change every 24 hours and game deals change every 12 hours (the previous group/batch of game deals is pushed down and lasts another 12 hours, so each group stays up 24 hours), so you are right. I don't know where JDelekto saw the 8 hours.