Perfume does not spoil like food, but it does age over time, and this can affect the color and original scent of it. Perfume is a complex mixture, and some ingredients may evaporate or oxidize with time. This changes the original chemistry of the scent.
Generally, perfume has a shelf life of three to five years, if kept tightly closed, in a cool place and out of direct sunlight. Heat and humidity are the two factors that cause the fastest aging of a perfume. Heat can evaporate key ingredients, while humidity can break down the chemical composition. Both environmental factors will alter the perfume.