I used this deal for my trip this year in late May. I booked it I believe early-mid April, and it had been being offered for some time before that. I checked and the offer started for bookings beginning on er March 16. It really is a great deal. It allowed me to stay on property (PPH). Hopefully they offer it again next year, as I would love to use it again. But Disney says they want to cut back on the deals they offer so who knows if it will be offered next year or not.
Another great deal if you want to stay on property is the 20-40% off hotel only deal. I did some figuring, and if the few extras you get with the package (priority seating, TTMM, lanyard and pin) are not that important to you, this deal is actually cheaper than the 5 for 3 day package. You have to buy tickets separately, but you can buy tickets only at the 5 for 3 day rate. You get 40% off GCH, 30% off DLH and 20% off PPH, so the better the hotel the more you save compared to getting the package.
Good luck and happy planning.