Shelf-life of Perfumes

I would like to start a seriously frank discussion on a subject that might be seriously scary to persons with large collections. My collection is now large enough for it to be seriously scary to me, so I am not here aloof scaring other people!

I will start be saying that on the whole the results are quite reassuring: my testing of my oldest 'fumes, the high prices often commanded by pre-reformulation specimens, and reports from persons who have one way or another gotten hold of some old bottle or other.

I do know that hard & fast good-storage rules are to keep it away from ultra-violet light, & any other ionising radiation (such as one's nuclear pile (doesn't everyone have one?)), and unheated in a way that, to speak technically puts it out of thermodynamic equilibrium. By this I mean that if you put it, say, on a hot surface, heat is being applied at one part, so that there is an 'enginry of heating' through the body of the stuff - and that would be _bad_; whereas if it is in a room of which the temperature gradually rises, the stuff is in a static condition, but its temperature just happens to be higher at a later time - and that is not so bad. (This is why some foodstuffs are baked in the oven - so that they become hot without departing much from thermodynamic equilibrium. We all know that you cannot bake bread by putting dough on a hotplate - you'll just get a mess. By the same token, non-equilibrium heating is _very bad_ for a perfume, whereas equilibrium heating is not so bad - but probably still a little bit bad at least.) So _don't_ put your perfume next to an intense localised heat-source!!

Anyway, I am _very_ keen to learn of the experiences of others at assaying of old specimens of perfume; I do not say 'glad' - I might well not be! - but please do lay it on anyway!

My experience with vintages has been mixed, so much so that I've given up on my quest for them altogether and happily go for modern takes such as Le Sillage Blanc instead. And, as I have no way of knowing how my vintage specimens had been kept before I got hold of them, I can only assume some may have had their stage of thermodynamic equilibrium disrupted along the way. Perhaps it was the nuclear pile in the garage.
https://youtu.be/9B0PaSznWJE - any more questions?

For what it's worth, out of my three Guerlain PdTs, Chamade is still in pristine condition. "Paloma Picasso / Mon Parfum (Eau de Parfum)", "La Nuit (Eau de Parfum)" and "Joy (Parfum)" unfortunately didn't fare well. "First (Eau de Parfum)" (pre-2000) and "N_5 (Parfum)" (late '70s/early '80s) are still beautiful, thought the latter is hinting at its finite life. But I don't see how this personal account would help drawing conclusions from as to the general shelf-life of perfumes. Perhaps an avid vintage collector can shed some light on the matter.

Chanel N°5 fræ the late 70s or early 80s ~hinting~ at its finite life? Sounds like pretty good news to me! Not so pleased to hear about the ones that didn't fare so well; but are these amongst those you got from other persons & are therefore of unknown curriculum vitæ? And then there are a couple of others that are fine or pristine. The emerging picture is not ^alarming^, by a long way! But hopefully I can gather a fair bit more evidence yet.

I know the exposition on thermodynamic equilibrium is a bit technical; but the distinction between something being heated in an unbalanced way (eg intensely at one part), and merely ^being^ at a higher temperature ^is^ a very important one. It's actually ^quite strongly^ analogous to the distinction between something receiving hammer blows, as opposed to it simply having a weight resting on it (respectively) - obviously the former is the more damaging in either case. The reason for putting a thermometer in the shade is of-a-piece with this; putting it in direct sunlight is rather like trying to measure the strength of a hammer-blow with a balance.

I'll leave-off these technical expositions now: but the point here is that the ~violence~ of the manner of heating is, at least within plausible bounds, more important than the final temperature attained. Definitey - do NOT leave a bottle of perfume on the top of a radiator or immediately in front of an incandescant heater!!

I forgot to mention in the ~stem~ or ~head~ of this thread that ~humidity~ is often cited as a deleterious agency; but I don't see how it can affect 'fume in a spray-bottle.