A deer's sense of smell is very keen. How can a buck trail a hot doe if it doesn't know which direction she is going? Ain't no arrows on the ground. He does it by following the oldest scent to the freshest. That same buck will know if the scent is a week old too. Kinda why they don't fear the spot you peed on a day or two later. So, keep the lid on and in the fridge between hunts. If I have much left over at the end of the season, I will actually put it in the freezer. Heat, and sunlight will breakdown scent too. There are preservatives put in most deer scents, but the best are still those the freshest. I wonder some times how many years some scents have been sitting in the back room of the sporting goods store. Why I tend to either buy what's been dated, what's new on the market this year, or go without.