Dear Saeid Hi

I am working on lethal effects of essential oils against insect pests. I preserve the essential oils sources in cool and dark places (to prevent thermal and solar degradation) after their dehydration (using an absorbent). thus they remain fresh and odorous for long time. 

Good luck!

Attars or Ittars are different from essential oils. Attars are cosmetic consumer products and are widely used in India as body perfumes. Flower essences are captured in sandalwood essential oil or other fixatives, matured and marketed in attractive bottles as attars. The (intense) odors of attars last for several hours.

Properly stored essential oils (filled up to the brim of glass or aluminum or stainless steel containers, tightly capped and kept in cool and dark places) retain their odor characteristics for a long time. Admixture of water, presence of oxygen, exposure to light etc. deteriorate the quality of essential oils. Deterpenation is another technique by which the shelf-life of essential oils can be prolonged by removing undesirable terpenes.

You may read some of my articles on the subject.

thanks, can you send some of them, please

I am attaching my papers on the subject of essential oil storage. I hope they will be useful to you.

I do not know how to answer your question and hope I will apprehend by dr. Rao attaches. But someway, there are "industrial" perfumes which get bad soon and "natural " perfumes (like Jo Malone's, Penhaligon's...) that NEVER go bad