I'll just chime in here to say that my mostly-lard soaps (they're 70%+) get to cure for at least 8 weeks, and because I don't add a chelator, their SF is almost exclusively 3% across the board. Also, I usually will add some kind of sugar to the lye-water, or to the fats. I particularly find that if I add a strong chamomile tisane (it's NOT a tea, folks!
), it adds a kind of caramel scent to the soap that becomes stronger the longer it cures. It also gives the soap a very creamy translucent sort of color.