Assuming you are talking about paint for a house:
If you want your paint to last, and to keep its original color and luster, it is important to store it properly. Paint should be stored in a cool, dry place, away from sunlight and heat sources. An unheated basement or shed is ideal. If you don't have access to a basement or shed, you can store paint cans in a closet or under a bed.
Paint cans should be stored upside down so the paint is in contact with the lid. This will prevent the paint from drying out and prevent the lid from rusting. If the paint can is not stored upside down, you can store the lid separately.
Paint should be used within two years of purchase. If it is older than that, it may not adhere to the surface properly or it may not have the same color.