A few thoughts...
Floral Absolutes can potentially degrade over time.
Floral EO’s / Ruhs / Ottos generally hold or improve with age.
Keep in mind that a “degraded oil” usually loses some top notes - but may deepen in the heart and base
Woods, roots, and resins generally improve with age.
I have some 140 year old lemon oil. No joke - 140 years old. Smells like lemon jam. No longer clean and sparkly. Now it is thick like crazy thaqueel Oud.
Some might call it degraded or oxidized. But it’s totally unique and smells friggen awesome.
My 2011 Mongolian Fried Musk Attar I made with a batch of 1940’s Mysore.
I have a small bottle of 1930.
And another small amount of 1860’s Mysore.
Guess what - they all smell incredible.
The 1860’s is likely oxidized as it was in a big bottle. It’s “degraded” and formed some notes reminiscent of vanilla. Similar to how old books start to smell vanillic. Heck - they used to synthesize vanillin from wood pulp. So makes total sense.
But - they haven’t gone bad. They smell insanely good.
Bushido uses a batch of Allspice EO from 1906. Still smells spicy - but more rounded and coumerinic.
Many of my Attars make use of old oils, and many of the Attar Bases (which I compound and then later add to Sandal) have been aging since 2011 and 2012, and I’m constantly making more batches to age for future use.
Aging may round off some top notes. It’ll deepen oils in the Heart and Base. But plenty of things don’t shift - or maybe a better way of saying is that they Mature - much in the same way that liquors, wines, and whiskeys do.
Consider also that age doesn’t always ruin notes. Sometimes it creates them. Can’t fake aged Scotch. Only age produces those tastes.
Many aged teas are considered medicine. They don’t produce the flavors or properties until they are decades old. Old teas found in attics and found in boxes in storehouses often yield insane treasures that sell for nutso prices.
Ironically - some of the newer style of Oud oils that are sold young and sparkly...give them a few years and although they’ll still be nice - notice that they may start smelling like other aged Ouds that for some reason are now getting shat on. That sparkle is due to youth. They’ll deepen with age.
People value age. With age comes Wisdom. Older oils may occasionally lose some of their sparkly youth - but often vast sums of money are spent on properly aged cheeses, wines, scotch / whiskey, coffee, tea - and even essential oils.