@PEARL I know my opinion would count as anecdotal evidence, but I can promise you my Borneo 50k sample changed enormously due to oxidation. As
@kesiro says the effect seems to vary from region to region: all my Borneos have clearly been affected by oxidation and none of my Hindis have.
@Nikhil S If you can smell the top notes then that is a good sign. Ceylon No. 1 projects very well, now better than ever in fact - I believe Taha wrote that the projection and longevity of his oils increases over time (up to six months).
But, I should say when I first smelled it it didn't seem to project at all, and this has been the case for me with a few Agar Aura oils (I have no idea why). In every single case, after giving it a couple of weeks my experience of the oils was completely different. This is entirely my personal opinion, but Taha's oils require more 'study time' than any other vendors', but that study time reaps an enormous reward. The way I wear them is just above the wrist bone, and at night - both factors seem to help with the appreciation of the oils. Ceylon No. 1 is a breathtakingly beautiful oil and it would be a shame if you weren't able to smell it at its best.