wfz on 13 June 2012
Daily deals are ... daily. Other regular price discounts tend to last a long time. I've never seen a discounted game become un-discounted.
You'll notice Amazon randomly slashes prices of games due to their price-matching service. If Toys R Us or some other store (Best Buy, etc) has a discounted price, Amazon will match that price. These deals MIGHT not last forever - I've never checked.
