Definition
Perceived longevity is the subjective duration of a fragrance as felt by the wearer, distinct from objective longevity measured in lab conditions on skin or on a mouillette. The wearer almost always underestimates the real duration: people nearby keep registering the trail long after the wearer has stopped noticing it on themselves (source: Sissel Tolaas, The Conversation).
Mechanisms
The central mechanism is olfactive fatigue, a neural adaptation: after 15 to 20 minutes of exposure to a constant odor, the brain filters the stimulus so it stays available for new signals. Selective anosmia to specific molecules (white musks, Iso E Super) widens the gap between felt duration and measured duration (source: Wikipedia, olfactory fatigue).
Skin chemistry, hydration and body heat amplify or compress diffusion. High molecular weight musks stay close to the skin and create a skin feel rated tenacious by people nearby but quiet for the wearer.
Use in perfumery
Reference phase boundaries frame any assessment: top 15 to 30 minutes, heart 2 to 4 hours, base 5 to 24 hours and beyond (source: Eisenberg, Memo Paris, Bon Parfumeur, convergent). Three techniques reset the perception: smell coffee beans, leave the room for a few minutes, ask a friend to confirm. For objective measurement, a mouillette left in the open air or a fabric test remain the recognized methods.