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The oils should be kept in a dark room at temperatures below 20 C. Or 68 F. It is also best to store in dark bottles labeling each bottle with the type of oil,the quantity, date, and possibly the yield this will make it easier if you plan on combining different mixtures but it is best to store oils in their pure form.

The fragrance actually fully develops after a few weeks to a month. The shelf life varies on the oil produced and some oils will solidify at temperatures below 8 C. Or 46.4 F. A safety warning Essential oils like alcohol are flammable and should be stored in a secure location.

Calculating yield:
[Oil volume (milliliters)/Plant mass (grams)] X100 = yield in percent:

Doing a little more research I found these calculations already done for us on the parent site. I would make an addendum that these yields vary depending on when the botanicals are harvested and how they are cut.
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Did you separate the oil from the hydrosols or do you store them together?

That's a good question, depends on the use. I plan to separate the lavender but keep the hydrosol of my mint.