Typically, holiday sales such as Easter, Christmas, Halloween, etc. last around 1-2 weeks. It all depends on Dacon, when he decides to end the sale, but typically it is 1-2 weeks at least. After this, there is still a permanent “sale” where the items appear as though they’re on sale, however the prices are just cheaper than they usually are (if that makes sense, lol).
Keep in mind you can also save up cubits and purchase items on the store with them at any time, sale or not. <3