Interesting point. When I first got it I gave it 5 stars for longevity. Then I started to think I couldn't detect it after a couple of hours. My wife who likes this scent (one of only few of mine she does like) often says how nice I smell some hours after applying it and when I can no longer smell it.
This may be a Guerlain phenomenon at least in my case. I find that the three I currently own either seem to come and go or disappear for me but others can still sense them?