Flash deals will come back, but I liked 24h flash deals. Shorter ones might be tough to handle for me especially when time is "not right", i.e. Halloween Sale is good on Halloween, but not very much a day later. Similarly Winter Sale overlapping with Christmas. It's good time for sale, but it's hard to keep track of short time flash sales and with what was mentioned some time ago, those flashes would start with 6h or 8h time period if I am right.
Oh right, Furrek posted link to those flash time periods I've just mentioned.