Why all day? The offers always change at the same time (10 am PST).
The items on sale seem constant, but the prices do appear to fluctuate. For example, the aforementioned Gothic games were 1.99 for Gothic2 Gold & Gothic3 at around noon. Now theyre 4.99 at 8:45pm.
I picked up Resident Evil 5 for like 12.50 the other day, just to see it go higher that evening. When you see an astounding deal on there, best to grab it whilst you can!