I'm not sure exactly what the reaction is, ie; why salt bars seem to do so much better after a long cure. I am really sensitive to coconut, do not exceed 18% in my regular bars (usually no more than 13-15%), but the high SF in salt bars (I also used full coconut milk, so it was even higher) made me think that they might work; they did not at a month out. But the cure - at least w/Shunt's - made a huge difference in the mildness/stripping-ness of the soap.
That does not entirely make sense to me logically (ie; it is the same amount of coconut, so the radical difference, even w/the length of cure, was surprising.) But the proof was definitely in the pudding with that one.
I usually cure my regular soaps for at least six weeks, but realistically, b/c I soap a lot and and do not sell, they end up getting cured for much longer. There is only so much soap one little woman can use, even giving it away in spades
I agree w/Spenny, though, test them at varying times. Many people here love their salt bars at a month out, and even more afterwards.