Whole mushrooms stay fresh for about seven to 10 days, while sliced mushrooms should be eaten within five to seven days for the best quality. Once cooked, mushrooms keep for an additional seven to 10 days.
Mushrooms should be stored in their original packaging; once opened, they can be stored in a paper bag for the longest shelf life and best quality. If mushrooms develop a sticky or slimy coating, this is a sign that they have spoiled and should not be eaten. To extend the shelf life of mushrooms, they can be cooked and then frozen for up to one month.