It is my opinion that the lasting power of a fragrance depends upon the fragrance. Some of my FO's last a very long time, a year or more, and others last only a few months. In M&P soap, FO's usually last longer than EO's, and in CP soap, EO's will usually perform better than FO's, in general. To my knowledge, there is nothing that you can do to make a fragrance last longer, you just learn over time which fragrances last and which don't. In my experience, the perfume duplicate FO's seem to lose their fragrance the fastest; other fragrances like cinnamon, etc., will last for 6-8 months or longer. As I said, I think it just depends upon the compostion of the individual fragrance oil.
Susan

Each FO and EO will have a lifespan of its own, but there are a couple of things you can do to make sure that the life of your oils will last.

- Store all of your oils in glass amber bottles and keep them away from heat and sunlight. This is much more true for EOs (because they are more volatile), but some FOs also contain essentials and therefore must be stored the same way.

- When purchasing EOs in large bottles, be sure to transfer them to smaller bottles leaving as little empty space at the top as possible. This will reduce their evaporation rate and will keep the scent more consistent throughout the whole bottle.

- Wrap your soaps entirely in a breathable material such as tissue paper or a paper soap box. This will lessen the rate that the scent dissipates, but still allow your soap to breathe as it continues to cure past the 2-4 week waiting period. If you'd prefer not to wrap them due to shrinking, place your soaps in a tupperware container after they've been allowed to sit out for 2-4 weeks.

- Try adding a little powdered benzoin to your soap (not for use in M&P). You can find it at Mountain Rose Herbs http://www.mountainroseherbs.com

Hope this helps!

Burgundy