Professeur de Parfums Roja Dove says perfume will last no longer than six months before starting to degenerate, so don't go saving it for special occasions.
To keep it in tip-top condition, don't have it out on display on your dressing table – sunlight and heat break it down. Instead store it in a cool, dark place.
When you apply it, 80 per cent of eau de toilette and 70 per cent of eau de parfum will have disappeared within four hours.
However, 50 per cent of pure perfume will still remain 24 hours later. So it's worth investing.